Journalof Speech and Hearing Research, Volume 34, 1197-1206, October 1991
Test Retest Reliability in Tympanometry Terry L. Wiley Kathryn A. Barrett University of Wisconsin-Madison
Test-retest reliability for tympanometric measures was evaluated across five sessions in 20 subjects with normal hearing and normal middle-ear function. Tympanograms were obtained on each ear for probe frequencies of 226, 678, and 1000 Hz using both ascending and descending directions of pressure change. Across all conditions, the tympanometric measure that consistently demonstrated the highest test-retest reliability was compensated static acoustic admittance. Test-retest correlations for peak compensated static acoustic admittance measures were higher than those for ambient measures across all probe frequencies and both directions of pressure change; the differences in correlations for peak and ambient measures, however, reached significance only for 226-Hz conditions. Across-session correlations for tympanogram width did not differ significantly for measures referenced to the lowest tympanogram tail and those referenced to +200 daPa. KEY WORDS: tympanometry, reliability, admittance
Acoustic immittance measures are routinely used in most audiology clinics (Martin & Sides, 1985). Tympanometric measures, for example, are integral parts of the test protocol in the "Guidelines for Screening for Hearing Impairment and Middle Ear Disorders" recommended by the American Speech-Language-Hearing Association (ASHA, 1990). In spite of the diagnostic value and popularity of acoustic immittance measures in clinical applications, there are limited data available on the variability and reliability of acoustic immittance measures over repeated trials and test sessions. Knowledge of test-retest reliability for acoustic immittance measures is particularly crucial inclinical applications. The determination of a pathologic condition or the need to monitor the progress or the remediation of a pathologic condition may require several evaluations on separate days. Accordingly, specification of normal limits in test-retest variability is necessary to determine whether changes in middle-ear function reflected in acoustic immittance measures are due to normal variation or to actual changes in pathologic condition. Published data regarding the test-retest reliability of acoustic immittance measures, however, are limited both in their availability and in their application. Tillman, Dallos, and Kuruvilla (1964), Nixon and Glorig (1964), and Feldman (1967) evaluated the reliability of acoustic immittance measures for normal subjects. In these earlier studies, however, only compensated static acoustic irnmittance measures were reported, and the measures were obtained with an instrument (Zwislocki Mechano-Acoustic Bridge) that is no longer commercially available. In addition, the probe frequencies used are not available on most current instruments. Liden, Peterson, and Bjorkman (1970) provided test-retest data for tympanometry in 3 normal adults. The authors used a custom-built instrument and reported test-retest data over 20 trials in a 10-hr period for a probe-tone frequency of 800 Hz. Tympanometric variables examined included notch depth (in dB), notch width (in mm), deviation of the tympanogram peak from 0 (in mm), and the difference (in dB SPL) "between the two endpoints of the tympanogram (p. 251)." These earlier data © 1991, American Speech-Language-Hearing Association
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0022-.4685/913405-1 197$0 1.00/0
1198 Journal of Speech and Heanng Research
are of limited current application because the primary data were presented in variables and units that cannot be applied to present clinical protocols and instruments, and the probe frequency of 800 Hz is not available on most currently available instruments. Feldman, Djupesland, and Grimes (1971) compared static compliance measures and compensated static acoustic impedance measures for a Zwislocki Acoustic Bridge and a Madsen (Z070) Electroacoustic Bridge, respectively. Eleven normal-hearing subjects experienced three trials for each instrument. High test-retest correlations between trials and between instruments were reported for the two sets of measures. Measures for the Madsen device were limited to compensated acoustic impedance magnitude (without associated phase angles) based on tympanometric values at ambient pressure and at +200 daPa. Such vector measures and the use of +200 daPa as a referent for ear canal contributions both result in significant error (Lilly & Shanks, 1981; Wiley & Block, 1979). Furthermore, these results reflect only on compensated static measures for a small sample of normal-hearing subjects. Porter and Winston (1973) reported reliability data for compensated static acoustic admittance measures on 16 normal-hearing subjects across five test sessions. Probe frequencies of 220 and 660 Hz were used. Acoustic susceptance was measured with pressure decreasing from +200 daPa, and acoustic conductance was measured with pressure increasing from -200 daPa. Values obtained at -200 daPa and ambient pressure or tympanometric peak pressure were used to calculate compensated static values. Means, standard deviations, and standard errors were reported for acoustic conductance and acoustic susceptance at probe frequencies of 220 and 660 Hz. Porter and Winston did not report the distribution characteristics of their static acoustic admittance data, but recent findings suggest that such data are positively skewed regardless of the referent for ear canal contributions (Wiley, Oviatt, & Block, 1987). Test-retest correlations reported by Porter and Winston were high for static measures referenced to tympanometric peak pressure. However, low test-retest correlation coefficients were reported for static measures referenced to ambient pressure, particularly for measures of acoustic conductance. Porter and Winston suggested that these low correlations reflected small shifts in the tympanometric peak pressure over time. The tympanometric peak pressure varied from test to test, although never more than 20 daPa. In addition, however, Wilson, Shanks, and Kaplan (1984) have reported increased complexity inthe configuration of tympanograms when an ascending direction of pressure change is used. The use of different directions of pressure change for obtaining acoustic conductance and acoustic susceptance tympanograms, then, also could have contributed to the increased variability in static acoustic conductance measures reported by Porter and Winston (1973). Finally, comparisons of the reliability between the two probe frequencies and the method for computation of static values for notched 660-Hz tympanograms were not presented. Reports of the test-retest reliability of acoustic immittance measures are few and are limited in clinical utility. Normal variations in most acoustic immittance measures across test
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October 991
sessions have yet to be established, particularly for more contemporary measures and instruments. Most past reports have been limited to compensated static acoustic immittance measures. Knowledge of the test-retest reliability and the limits of normal variance in acoustic immittance measures is crucial in making clinical decisions regarding the status of middle-ear function based on acoustic immittance measures. Thus, the purpose of this study was to quantify the normal test-retest reliability and variability for acoustic admittance measures across test sessions.
Method Subjects Twenty normal-hearing young adults (10 females, 10 males) between the ages of 18 and 25 years served as subjects. All subjects presented a negative history of otologic disease, particularly during adulthood. The subjects were primarily recruited from the undergraduate and graduate student population at the University of Wisconsin-Madison. All subjects had normal hearing and normal middle-ear function based on behavioral audiometry, tympanometry, and contralateral acoustic reflex measures. Normal hearing was defined as auditory thresholds equal to or less than 10 dB HL (ANSI, 1989) for tones of 500, 1000, 2000, 4000, and 8000 Hz in both ears. All subjects also presented normal acoustic admittance tympanograms, acoustic reflex thresholds for a 1000-Hz activator, and compensated static acoustic admittance values for a 226-Hz probe (Wiley et al., 1987). Test Measures All test measures were obtained in a sound-treated room (Industrial Acoustics Corporation, 1200 Series, #101539). Each subject participated in five test sessions scheduled no less than 24 hr and no more than 7 days apart. Acoustic admittance tympanograms were obtained on each ear for independent probe frequencies of 226, 678, and 1000 Hz. Both ascending (-400 daPa to 400 daPa, -/+) and descending (400 daPa to -400 daPa, +/-) directions of pressure change were used to obtain tympanograms at each probe frequency. Thus, tympanograms for the following six conditions were obtained for each ear during each of the five test sessions: 226 Hz, +/-; 226 Hz, -/+; 678 Hz, +/-; 678 Hz, -/+; 1000 Hz, +/-; and 1000 Hz, -/+. The acoustic immittance system used for obtaining the experimental measures enabled representation and analysis of tympanograms in polar (acoustic admittance and phase angle) and rectangular (acoustic conductance and acoustic susceptance) forms. The order of conditions was randomly assigned without replacement for each ear and session. The first ear tested (right or left) was randomly selected at the beginning of the initial test session and alternated for the remaining four sessions. The probe unit and tip were removed from the ear canal immediately following a set of three tympanometric trials. A rest interval of approximately 5 min preceded reinsertion of the probe tip for each ear.
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Wiley & Barrett: Test-Retest Reliabty
Instrumentation Behavioral thresholds for tones were obtained with a diagnostic audiometer (Grason-Stadler, GSI 16) calibrated in accordance with ANSI (S3.6-1989) specifications. All acoustic immittance measures were obtained using a softwaredriven acoustic immittance system (Nicolet, Aurora, Middle Ear Analyzer, Version 4.20) calibrated according to ANSI (S3.39-1987) specifications for Type I Aural Acoustic Immittance Instruments. The measured pump speed of the acoustic immittance instrument was 50 daPa/s.
Data Analysis Test-retest reliability for peak pressure, compensated static acoustic admittance measures, and tympanogram width were evaluated across test sessions for each direction of pressure change and for each probe frequency. All tympanograms were obtained in a measurement-plane mode. Compensated static acoustic admittance values were determined using peak and ambient pressure referenced to the lowest tail value and to the value at +200 daPa. Tympanogram-width measures were calculated using the value at peak pressure in reference to both the lowest tail value (Koebsell & Margolis, 1986) and the value at +200 daPa (Koebsell, Shanks, Cone-Wesson, & Wilson, 1988). Testretest reliability for each measure across sessions was evaluated using Pearson product moment correlations.
Results Tympanometric Data Averaged data across sessions for each tympanometric variable and experimental condition are shown in Table 1. Each tabled value is based on measures across five sessions, 20 subjects, and two ears (200 total measures). Based on the earlier finding (Wiley et al., 1987) that tympanometric measures are positively skewed, a nonparametric test (sign test) was performed on all variables and conditions for the right and left ears. Sign-test results indicated that only 16 out of 450 measures were significantly different for the two ears. This outcome is within a Type-I error of 5%. As a result, the data for all measures and conditions were collapsed across ears for presentations and statistical analyses. Tympanogram width is reported only for tympanograms obtained with the 226-Hz probe. At higher probe frequencies, tympanogram notching occurred for different subjects within the group and the presence of notching substantially altered tympanogram-width estimates for these subjects. Further, reported norms and clinical applications of tympanogramwidth measures presently are limited to measures for a 226-Hz probe frequency (ASHA, 1990). Session-to-session variability. In addition to measures of central tendency across sessions for each variable, Table 1 includes the 90% range of values across sessions, the mean difference across sessions, and a ratio of the variance to the mean (90% range/mean). The range was used as a measure of dispersion given past work (Wiley et al., 1987)
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demonstrating skewed distributions for the variables of interest. The 90% range/mean ratios are provided as a means of evaluating differences in variance for test variables with different units and dimensions of measure. Also, this measure (90% range/mean ratio) enables, comparison of sessionto-session variability and test-retest reliability for measures that have similar ratios. The variability across sessions differed considerably for variables and for probe frequency. Across-probe frequencies and directions of pressure change, acoustic conductance, and acoustic admittance measures evidenced the least variability and the lowest and most stable 90% range/mean ratios. Only acoustic conductance, acoustic admittance, and peak pressure offered similar 90% range/mean ratios across the two directions of pressure change and across the three probe frequencies. Other measures, particularly acoustic susceptance and phase angle measures, demonstrated increased variability and higher 900/c range/mean ratios at higher probe frequencies. In general, peak measures evidenced less session-tosession variability and lower 90% range/mean ratios relative to ambient, compensated measures. This was particularly evident for 678-Hz and 1000-Hz probe frequencies. Finally, across all variables, session-to-session variability and 90% range/mean ratios were least for a 226-Hz probe relative to higher probe frequencies. Tympanogram notching. The complexity of tympanometric patterns increased with increased probe frequency (Table 2). Only single-peaked tympanograms were observed at a probe frequency of 226 Hz; notched tympanograms were observed in a substantial number of cases for 678- and 1000-Hz probes. This likely accounts for the increased session-to-session variability observed at the higher probe frequencies (Table 1). In contrast to Wilson et al. (1984), who reported a greater number of notched tympanograms at a probe frequency of 678 Hz for a negative-to-positive (-/+) direction of pressure change than for a positive-to-negative (+/-) direction, little difference in the number of notched tympanograms for the two directions of pressure change using a 678-Hz probe was noted in the present study. At a probe frequency of 1000 Hz, we did observe a greater number of notched tympanograms for the -/+ direction of pressure change than for the +/- direction. The session-to-session variation in tympanogram pattems for 678-Hz and 1000-Hz probe frequencies is summarized in Table 3. The tympanogram types or shapes are those of Vanhuyse, Creten, and Van Camp ('1975) for acoustic conductance and acoustic susceptance tympanograms. The total for each tympanogram type was relatively stable across the five sessions. The session totals, however, do not reflect the shifts in tympanogram patterns for individual subjects across sessions. These shifts influence test-retest reliability and session-to-session variability. A tabulation of session-tosession shifts in tympanogram category is provided in Table 4. Most shifts from one pattern to another across the five sessions were limited to one category. Specifically, sessionto-session pattern shifts across both 678-Hz and 1000-Hz probes for both directions of pressure change were -+1 category in 85% of the cases. A shift in excess of two categories was observed in only one case. For both probe
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TABLE 1. Means (M), medians, mean differences (M DIFF), 900% ranges and 90% range/M ratios across sessions and ears for measures obtained under conditions of probe-frequency and direction-of-pressure change.
Variable
M
Ambient Ga Peak Ga Ambient Ba Peak B Ambient Ya Peak Ya Ambient Ya (+200) Peak Y, (+200) Ambient y Peak 4by Ambient by, (+200) Peak by (+200) Tympanogram width Tympanogram width (+200) Peak pressure
.30 .34 .58 .76 .66 .84 .51 .69 62 66 58 64 103 79 23
Ambient Ga Peak Ga Ambient Ba Peak Ba Ambient Ya Peak Ya Ambient Ya (+200) Peak Ya (+200) Ambient by Peak ,by Ambient by (+2 0 0) Peak by (+200) Peak pressure
1.55 2.11 .15 .80 1.72 2.37 1.66 2.15 10 20 -13 5 27
Ambient Ga Peak Ga Ambient Ba Peak Ba Ambient Ya Peak Ya Ambient Ya (+200) Peak Y, (+200) Ambient by Peak y Ambient (by (+200) Peak by (+200) Peak pressure
2.29 3.00 -. 09
1.35 2.67 3.85 2.97 3.10 5.00 24.0 -32 0 47
Median
M DIFF
90%/o
90% R
Condition: 226-Hz Negative-to-positive .28 .003 .10-.53 .29 .005 .12-.62 .51 .009 .29-1.14 .68 .010 .38-1.39 .61 .009 .32-1.23 .77 .006 .43-1.48 .46 .009 .21-1.02 .61 .007 .34-1.28 63 .06 46-79 67 .46 51-81 57 .06 41-80 64 .57 47-83 105 .28 60-145 80 25
.81 1.16
45-110 -5-45
R/M
M
1.43 1.47 1.47 1.33 1.38 1.25 1.59 1.36 0.53 0.45 0.67 0.56 0.83
69 69 64 63 110
0.82 2.17
80 -13
Condition: 678-Hz Negative-to-positive 1.35 .047 .70-2.84 1.38 1.94 .006 1.01-3.61 1.23 .27 .022 -1.26-1.38 17.6 .71 .041 -. 24-2.44 3.35 1.44 .051 .82-3.26 1.42 2.09 .008 1.16-4.05 1.22 1.41 .066 .76-3.32 1.54 1.9 .001 1.07-3.86 1.30 11 .34 -36-44 8.00 22 .02 -70-45 5.75 -10 .34 -48-24 5.54 5 .57 -23-3 11.60 30 .91 -5-45 1 85 Condition: 1000-Hz Negative-to-positive 2.36 .04 0-4.25 1.86 3.05 .06 .65-5.33 1.56 .03 .06 -. 24-2.0 24.89 1.02 .12 -.83-5.34 4.57 2.50 .02 .93-5.02 1.53 3.80 .07 1.84-6.74 1.27 2.61 .01 1.1-5.79 1.58 3.12 .06 .86-5.3 1.43 1.00 2.01 -37-75 22.40 21.0 1.38 -11-80 3.79 -32 .29 --70-3 2.28 0 .06 -34-28 45 1.00 10-105 2.02
.26 .31 .70 .79 .75 .86 .61 .72
1.97 2.25 .41 .36 2.12 2.38 1.86 2.14 13 10 2 --3 -13 2.87 3.25 .07 .76 3.18 3.70 3.35 3.38 7 17
-16 -4 9
Median
M DIFF
90%o
90% R
Condition: 226-Hz Positive-to-negative .25 .004 .05-.54 .29 .004 .11-.57 .64 .011 .34-1.25 .74 .014 .43-1.3 .70 .009 .38-1.32 .80 .012 .45-1.38 .56 .007 .26-1.06 .68 .009 .36-1.16 71 .75 54-84 70 .69 54-80 64 .92 45-77 63 .75 46-77 108 1.06 70-155 80 -5
.03 1.09
55-110 -40-5
R/M 1.88 1.48 1.30 1.10
1.25 1.08 1.31 111
0.43 0.38 0.50 0.49 0.77 0.69 -3.46
Condition: 678-Hz Positive-to-negative 1.85 .018 .89-3.33 2.11 .019 1.17-3.67 .42 .023 -.54-1.52 .34 .033 -.90-1.64 1.98 .020 1.12-3.40 2.28 .009 1.30-3.90 1.75 .013 .89-3.17 198 .014 1.16-3.58 12 .40 -21-44 9 .97 -17-37 -1 .17 -32-27 -23 .75 -30-25 -5 1.16 -40-5
1.24 1.11 5.02 7.06 1.08 1.09 1.23 1.13 5.00 5.40 29.50 18.33 3.46
Condition: 1000-Hz Positive-to-negative 2.91 .066 .19-4.86 3.44 .057 .51-5.58 .33 .03 -2.63-1.69 .78 .06 -1.23-3.92 3.21 .066 1.03-5.10 3.69 .03 2.03-5.60 3.54 .02 1.23-5.40 3.39 .01 1.28-5.75 6 1.01 -35-54 14 1.38 -14-76 -13 .17 -54-17 -3 1.66 -29-21 5 .06 -45-65
1.63 1.56 61.71 6.78 1.28 0.96 1.24 1.32 12.71 5.29 4.44 12.50 12.20
Note. All values for Ga, Ba,,Y and 4y, are compensated static measures. The values for Ga, Ba, and Ya are in mmhos, values for by are in degrees, and values for tympanogram width and peak pressure are in daPa. Each tabled value is based on 200 measures (5 sessions/2 ears/20 subjects). Tympanogram-width measures are provided only for the 226-Hz probe conditions. Mean differences are the mean of mean differences across the five sessions for each variable. frequencies, the number of shifts for a positive-to-negative direction of pressure change was greater than that for a negative-to-positive direction.
Test-Retest Reliability Test-retest correlations for each probe frequency are shown in Table 5. Mean correlations for each ear, direction of pressure change, and tympanometric variable between sessions are provided. The grand mean in each table represents the mean of mean correlations across right and left ears. The
90% range refers to the upper (95%) and lower (5%) limit of correlations across both ears. Pressure direction.Mean correlations for each ear, grand mean correlation values, and the ranges of correlations suggested similar test-retest reliability for the two directions of pressure change for each probe frequency. The mean difference in correlations across all tympanometric variables and across the two directions of pressure change were 0.06 for 226 Hz, 0.12 for 678 Hz, and 0.08 for 1000 Hz. Ambient versus peak measures. Test-retest reliability, as reflected in session-to-session correlations, was similar
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Wiley & Barrett: Te:st-Retest Reliabhlity
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TABLE 2. Number and percentage of tympanogram patterns for each condition across ears. Numbers and percentages for each probe frequency and direction of pressure change (+/and -/+) and the grand totals and percentages are displayed. The classification of tympanogram patterns Is that reported by Vanhuyse, Cretan, and Van Camp (1975). Shape/Condition
1B1G
226 Hz 226 +/226-/+ Total Percent 678 Hz 678 +/678 -/+ Total Percent 1000 Hz 1000 +/1000 -/+ Total Percent Total Percent
3B1 G
3B3G
5B3G
Other
Total
0 0 0 0%
200 200 400
200 200 400 100%
0 0 0 0%
0 0 0 0%
0 0 0 0%
42 49 91 23%
145 140 285 71%
4 4 8 2%
7 6 13 3%
2 1 3 1%
200 200 400
22 2 24 6%
163 167 330 83%
14 28 42 11%
1 1 2 < 1%
0 0 0 0%
200 198 398
515 43%
615 51%
50 4%
15 1%
3 .05] or positive-to-negative [t(17) = 0.49, p > .05] direction of pressure change. Probe frequency. As is evident from Figure 1, test-retest reliability varied across probe frequency for all compensated static measures. Peak compensated static acoustic admittance measures demonstrated good test-retest reliability across all three probe frequencies. The reliability of acoustic conductance and acoustic susceptance measures, however, varied considerTABLE 4. Shifts In tympanogram categories for each condition (probe frequency and direction of pressure change) across the five sessions and across the 40 ears. Number of shifts Shifts in category
678 Hz -/+
678 Hz +/-
1000 Hz -/+
1000 Hz +/-
+3 +2 +1 -1 -2
0 2 14 15 2
0 6 16 13 5
0 0 10 8 0
1 0 13 15 2
Note. The entries for shifts represent the number of positive or negative category shifts from session to session. A positive shift indicates increased tympanogram notching, and a negative shift indicates a shift to a tympanogram category with less notching.
TABLE 3. Number of each tympanogram pattern (shape) across sessions for 678-Hz and 1000-Hz probes and for both directions (-/+ and +/-) of pressure change. The tympanogram shape categories are those of Vanhuyse, Cretan, and Van Camp (1975). 678 Hz -/+ Session
678 Hz +Session
1000 Hz -/+ Session
1000 Hz +/Session
Shape
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1B1G 3B1 G 3B3G 5B3G Other Total
8 30 1 1 0 40
11 26 3 0 0 40
10 27 0 2 1 40
13 26 0 1 0 40
8 30 0 2 0 40
8 30 1 1 0 40
9 29 0 1 1 40
8 28 1 2 1 40
10 29 1 0 0 40
7 29 1 3 0 40
0 38 2 0 0 40
1 33 6 0 0 40
0 33 6 0 1 40
1 30 8 1 0 40
0 34 6 0 0 40
2 36 2 0 0 40
7 28 5 0 0 40
6 30 4 0 0 40
3 35 1 1 0 40
5 33 2 0 0 40
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TABLE 5. Mean correlations for both right and left ears, correlation grand means and correlation ranges across five sessions for measures obtained under conditions of probe-frequency and direction-of-pressure change.
Variable Ambient Ga Peak Ga Ambient Ba Peak Ba Ambient Y, Peak Ya Ambient Y. (+200) Peak Y (+200) Ambient $y Peak y Ambient $y (+200) Peak y,(+200) Tympanogram width Tympanogram width (+200) Peak pressure Ambient Ga Peak Ga Ambient Ba Peak Ba Ambient Ya Peak Y Ambient Ya (+200) Peak Y, (+200) Ambient 1y Peak 0y Ambient (4y(+200) Peak $y(+200) Peak pressure Ambient Ga Peak Ga Ambient Ba Peak Ba Ambient Ya Peak Ya Ambient Ya (+200) Peak Ya (+200) Ambient Iy Peak y Ambient y, (+200) Peak 4y (+200) Peak pressure
Right
Left
Grand Mean
Range
Right
Left
Grand Mean
Range
Condition: 226-Hz Negative-to-positive .52 .38 .45 .14-.64 .42 .39 .41 .20-.55
.68 .53
.73 .90
.65 .86
.69 .88
.17-.91 .77-.93
.83 .85
.74 .81
.79 .83
.74 .88
.63 .83
.68 .86
.12-.91 .72-.91
.83
.72
.78
58-.90
.83
.80
.82
.68-.93
.69
.63
.66
.09-.90
.90 .49 .44 .38 .46 .72 .54
.86 .38 .42 .24 .41 .56 .48
.88 .43 .43 .31 .44 .64 .51
.79-.92 .16-.61 .30-.60 .10-.54 .22-.62 .25-.84 .24-.72
.83 .86 .62 .57 .54
.71 .79 .30 .36 .30
.77 .83 .46 .47 .42
.57-.89 .67-.92 .23-.73 .28-.67 .09-.72
.55
.41
.48
.18-.69
.69
.46
.58
.43-.80
.70 .68 .65
.62 .47 .29
.66 .58 .47
.45-.86 .39-.79 - 33-.75
Condition: 678-Hz Negative-to-positive .68 .66 .67 .53-.78 .46 .80 .63 .12-.90 .39 .74 .57 -.16-.88 .12 .61 .37 -. 10-.92 .71 .71 .71 .57-.85 .51 .87 .69 .12-.93 .60 .71 .66 .33-.81 .47 .77 .62 .07-.91 .50 .81 .61 .15-.90 .30 .60 .45 -. 03-.91 .45 .78 .62 .03-.88 .31 .69 .50 .03-.89 .50 .54 .52 .04-.83 Condition: 1000-Hz Negative-to-positive .29 .75 .52 -. 18-.94 .34 .84 .59 -.18-.90 .19 .25 .35 .64 .43 .56 .31 .18 .31 .37 .32
.38 .67 .57 .86 .68 .81 .45 .72 .73 .39 .90
.29 .46 .46 .75 .56 .69 .38 .45 .52 .38 .61
-. 11-.69 -. 29-.82 - .05-.79 .42-.93 .02-.78 .34-.90 - .05-.81 -. 37-.85 - .30-.92 .05-.83 -. 16-.94
.83 .83 .67 .63 .86 .87 .81 .83 .79 .71
Condition: 226-Hz Positive-to-negative .38 .54 .16-.73 .43 .48 .22-.61 .57-.90 .69-.93
Condition: 678-Hz Positive-to-negative .79 .81 .65-.91 .80 .82 .74-.92 .29 .48 .07-.81 .32 .48 .11-.78 .85 .86 .68-.91 .87 .87 .82-.94 .72 .77 .54-.87 .78 .81 .68-.88 .59 .69 .44-.90 .55 .63 .36-.82
.74
.60
.67
.50-.90
.66 .70
.56 .67
.61 .69
.34-.78 .59-.74
Condition: 1000-Hz Positive-to-negative .45 .62 .49
.48 .44
.80 .79
.74 .40 .42 .79 .44 .81
.52
.49
-. 10-.84
.63 .53 .55 .50 .58 .39 .45 .49 .65 .63
.63 .51 .52 .47 .69 .59 .60 .45 .54 .71
-. 15-.89 -.07-.91 --.06-.85 .01-.82 -.07-.91 .02-.90 - .26-.85 -.08-.85 -.07-.89 .02-.93
.57
.51
.17-.80
.50
.66
- .28-.92
Note. Correlations for each ear are based on 100 measures (5 sessions/20 subjects). The grand mean correlation is the mean of mean correlations for the five sessions and is based on 200 measures (5 sessions/20 subjects/2 ears); the range is based on both right and left ear correlations across five sessions. ably across probe frequencies. Comparatively, for example, acoustic conductance measures demonstrated higher reliability at 678 Hz for both ambient (r = .74) and peak (r = .73) conditions than did corresponding measures of acoustic susceptance (ambient r = .53, peak r = .43). Acoustic susceptance measures, however, evidenced higher test-retest reliability at 226 Hz for ambient (r = .74) and peak (r = .86) conditions relative to acoustic conductance measures (ambient r = .50, peak r = .45). Like acoustic admittance measures, component measures referenced to the tympanometric peak typically were superior in reliability to ambient measures. Test-retest reliability for admittance phase angle also varied across probe frequency; peak measures of admittance phase angle evidenced more stable
test-retest reliability across probe frequency relative to ambient phase angle measures.
Discussion ------The primary purpose of the present study was to evaluate the session-to-session reliability for tympanometric measures used in clinical practice. Reports on such test-retest reliability have been few and, further, have been limited in application with respect to present clinical protocols. As was noted in the introduction, it is not feasible or appropriate to compare data from most of the earlier studies with data
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Wiley & Barrett: Test-Retest Reliability
a
1.0
10
08
0.8
1203
e 0.6
0.6
z < 0.4
m 0.4
02
02
o P1000 [] P678 * P226
00 G
B
Y
O P1000 1 P678 * P226
00 Y
PH
Y2
PH
PH2
TW
TW2
MEASURE
MEASURE 1.0
10
0.8
0.8
a 0.6
.o 06
Z 04
Z 04
D
02
02
o
oCP1000
P1000 El P678 * P226
[] P678 0.0
* P226 G
B
Y
0.0 Y
PH
obtained from current instrumentation such as that used in the present study. A limited exception is the work of Porter and Winston (1973). Porter and Winston reported test-retest correlations for compensated static acoustic conductance and acoustic susceptance measures across five sessions in 16 "normal-hearing" subjects "with presumably normal middle ears" (p. 142). Data referenced to both peak and ambient pressures were provided. Figure 3 shows mean correlations from the Porter and Winston work and corresponding correlations from the present study. In conformity with the procedures used by Porter and Winston, acoustic conductance data in Figure 3 for the present study are limited to mean correlations for the negative-to-positive direction of pressure
PH
PH2
TW
TW2
MEASURE
MEASURE
FIGURE 1. Grand mean correlations (across the five sessions) for peak (top panel) and ambient (lower panel) compensated static measures at probe frequencies of 226 (P226), 678 (P678), and 1000 (P1000) Hz. All compensated values are referenced to the lowest tall of the tympanograms. Correlations are based on acoustic conductance (G), acoustic susceptance (B), acoustic admittance (Y), and admittance phase angle (PH) measures averaged across both ears and both directions of pressure change.
Y2
FIGURE 2. Grand mean correlations (across the five sessions) for peak (top panel) and ambient (lower panel) compensated static acoustic admittance (Y)and admittance phase angle (PH) at probe frequencies of 226 (P226), 678 (P678), and 1000 (P1000) Hz. Variables associated with the descriptor 2 were based on ear canal corrections referenced to +200 daPa, and all others were based on the lowest tympanogram tail. Tympanogram-
width (TW) measures, limited to the single probe frequency of 226 Hz, also are Included. Correlations are based on means for each measure across both ears and both directions of pressure change. change, and data for acoustic susceptance are for the positive-to-negative direction of pressure change. Also, Porter and Winston used 220- and 660.-Hz probe frequencies; comparable data from the present study are based on probe frequencies of 226 and 678 Hz. Clearly, as Figure 3 illustrates, there are substantial differences in reported test-retest reliability for the two studies. With the exception of ambient compensated static acoustic conductance measures at 226 (or 220) Hz, reliability correlations for the present study are lower than those reported by Porter and Winston. Also, the substantial differences in test-retest reliability for peak and
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1204
Journal of Speech and Heanng Research
1.0
0.8
>
0.6
Z 0.4
Z 0.2
0.0 GA
GP
BA
BP
MEASURE 1.0
_ 0.6
Z 0.2
0.0 GA
GP
BA
BP
MEASURE
FIGURE 3. Correlations for peak (P) and ambient (A) compensated static acoustic conductance (G) and acoustic susceptance (B) from Porter and Winston (1973) and from the present study. For both sets of data, acoustic conductance measures were obtained using a negative-to-positive direction of pressure change, and acoustic susceptance measures were obtained with a positive-to-negative direction of pressure change. The Porter and Winston data are mean correlations for probe frequencies of 220 (PW 220) and 660 (PW 660) Hz. Data for the present study are grand mean correlations (across the five sessions) at probe frequencies of 226 (WB 226) and 678 (WB 678) Hz. Correlations for the present study were based on compensated values referenced to the lowest tail of tympanograms. ambient measures reported by Porter and Winston were not observed in the present study. The disparity in test-retest reliability across the two studies is most apparent at the higher probe frequency (660 or 678 Hz). This may be due, in part, to differences in data analyses for notched tympanograms. In the present study, notched tympanograms were observed in a substantial number of cases for 678- and 1000-Hz probes (Table 2). Indeed, tympanogram notching and shifts in tympanogram categories across session (Tables 3 and 4) likely contributed heavily to the reduced test-retest reliability for acoustic admittance components
34
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ctober 1991
(acoustic conductance, acoustic susceptance, acoustic admittance, admittance phase angle) at higher probe frequencies approximating the resonance frequency of the middleear transmission system. As expected, this effect was most dramatic for the reactive component (acoustic susceptance). Porter and Winston did not report whether notched tympanograms were observed in their subject group for the 660-Hz probe, nor did they report the calculation method for deriving compensated static values in such cases. If Porter and Winston excluded cases of notched tympanograms or if they did not use the notch as a basis for compensated calculations, less variability across sessions might have resulted. Regardless of the specific source(s) for differences in the two studies, our present results are not consistent with the high test-retest reliability in acoustic admittance components or the substantial superiority in test-retest reliability for compensated peak measures relative to ambient measures originally reported by Porter and Winston. In the present study, correlations for peak compensated measures typically were higher than those for ambient measures. However, our test-retest correlations were generally lower and the differences in peak and ambient correlations were generally much smaller than those reported by Porter and Winston. Across all conditions (probe frequency, ear, direction of pressure, and ear canal reference), the tympanometric measure that consistently demonstrated the highest test-retest reliability in the present study was compensated static acoustic admittance. Peak compensated acoustic admittance measures were superior to ambient measures in terms of session-to-session variability (Table 1) and in terms of test-retest reliability (Table 5). Two-tailed tests of significance on dependent correlations (Bruning & Kintz, 1977, pp. 215-217) were performed on the correlations (Table 5) for compensated static peak and ambient acoustic admittance referenced to both the lowest tympanometric tail and +200 daPa for all three probe frequencies. Significant dependent correlations were obtained only for the 226-Hz probe using a negative-to-positive direction of pressure change. Acrosssession correlations for peak static measures were significantly different from those for ambient measures in the case of both +200 daPa [t (17) = 2.92, p < .05] and lowest tail [t (17) = 2.51, p < .05] ear canal referents. In all cases, test-retest correlations for peak measures were higher than those for ambient measures. Peak compensated static acoustic admittance and tympanogram width are primary acoustic immittance measures recommended by the American Speech-Language-Hearing Association (1990) for screening of middle-ear function. If acoustic admittance measures are restricted to a low-frequency probe (226 Hz), as in the ASHA guidelines for screening, these two measures offer different degrees of test-retest reliability according to the present study. A summary of mean across-session correlations for basic tympanometric measures at 226 Hz from the present study is provided in Figure 4. Correlations for peak compensated static acoustic susceptance and acoustic admittance are high, indicating very good test-retest reliability. Here, only peak data are provided on the basis of the analysis demonstrating higher test-retest reliability for peak measures relative to ambient measures. The close agreement in test-retest
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Wiley & Barrett: Tes:-Retest Rehability
reliability for acoustic susceptance and acoustic admittance measures is not surprising for a 226-Hz probe frequency; at low probe frequencies the middle-ear transmission system is stiffness-controlled for normal subjects. Test-retest reliability for tympanogram-width measures, using either lowest tail or +200-daPa referents, is lower than that for compensated static acoustic admittance measures. Peak pressure, admittance phase angle, and acoustic conductance measures evidence even lower test-retest reliability than that observed for tympanogram width. Finally, it should be understood that the lower overall test-retest reliability observed for acoustic conductance, acoustic susceptance, and admittance phase angle does not necessarily indicate that these particular measures are without diagnostic significance. Complex interactions between
these components, such as those that occur at frequencies approaching resonance for the middle-ear transmission system, may result in decreased session-to-session reliability. Within a session for a given subject and across sessions for a given subject, however, the characteristics and frequency loci of the interactions may be quite useful in diagnostic applications. Differences in middle-ear resonance for a subject relative to normative data and shifts in middle-ear resonance over time, for example, may be useful diagnostic indices. Similarly, the lower test-retest reliability for tympanogram-width measures may actually underlie sensitivity of the measure to changes in tympanogram characteristics associated with subtle changes in middle-ear mechanics. These changes, in turn, may be useful in diagnostic applications and in monitoring middle-ear function.
.4
1.0
0.8
0-0
0.6
Pq1
Z
0.4
W
0.2
[] P200 LT
0.0 G
B
Y
1205
PH TW PPR
MEASURE (226 Hz) FIGURE 4. Grand mean correlations (across the five sessions) for acoustic conductance (G), acoustic susceptance (B), acoustic admittance (Y), admittance phase angle (PH), tympanogram width (TW) and peak tympanogram pressure (PPR) at a probe frequency of 226 Hz. All acoustic admittance measures (G,B,Y, PH) are peak compensated static means across both directions of pressure change. The filled bars represent ear canal corrections referenced to the lowest tympanogram tail; hatched bars represent ear canal corrections referenced to +200 daPa.
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1206
Journal of Speech and Heanng Research
Acknowledgments The authors wish to thank Dee K. Vetter for her advice regarding statistical analyses, Scott Rose for necessary software development, and Nicolet Instrument Corporation, Madison, WI, for the use of the Aurora system used in data collection. A paper based on portions of this research was presented at the 1989 Annual Convention of the American Speech-Language-Hearing Association in St. Louis, Mo.
References American National Standards Institute. (1987). American National Standard specifications for instruments to measure aural acoustic impedance and admittance (aural acoustic immittance) (ANSI S3.39-1987). New York: ANSI. American National Standards Institute. (1989). American National Standard specification for audiometers (ANSI S3.6-1989). New York: ANSI. American Speech-Language-Hearing Association (ASHA). (1990). Guidelines for screening for hearing impairment and middle ear disorders. Asha, 32(Suppl. 2), 17-24. Bruning, J. L., & Klntz, B. L. (1977). Computational handbook of statistics (2nd ed.). Glenview, IL: Scott, Foresman Feldman, A. (1967). Acoustic impedance studies of the normal ear. Journal of Speech and Hearing Research, 10, 165-176. Feldman, A., Djupesland, G., & Grimes, C. T. (1971). A comparison of impedance measurements with mechanical and electroacoustic impedance measuring devices. Archives of Otolaryngology, 93, 416-418. Koebsell, K. A., & Margolis, R. H. (1986). Tympanometric gradient measured from normal preschool children. Audiology, 25, 149157. Koebsell, K. A., Shanks, J. E., Cone-Wesson, B. K., & Wilson, R. H. (1988). Tympanometric width measures in normal and pathologic ears. Asha, 30, 99 (Abstract No. 10).
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Liden, G., Peterson, J. L., & Bjorkman, G. (1970). Tympanometry. Archives of Otolaryngology, 92, 248-257. Lilly, D.J., & Shanks, J. E. (1981). Acoustic immittance of an enclosed volume of air. In G. Popelka (Ed.), Hearing assessment with the acoustic reflex (App. B, pp. 145-160). New York: Grune & Stratton. Martin, F. N., & Sides, D. G. (1985). Survey of current audiometric practices. Asha, 27, 29-36. Nixon, J. C., & Glorig, A. (1964). Reliability of acoustic impedance measurements of the eardrum. Journal of Auditory Research, 4, 261-276. Porter, T. A., & Winston, M. E. (1973). Reliability of measures obtained with the otoadmittance meter. Journal of Auditory Research, 13, 142-146. Tillman, T. W., Dallos, P. J., & Kuruvilla, I. (1964). Reliability of measures obtained with the Zwislocki acoustic bridge. Journal of the Acoustical Society of America, 36, 582-588. Vanhuyse, V. J., Creten, W. L., & Van Camp, K. J. (1975). On the W-notching of tympanograms. Scandinavian Audiology, 4, 45-50. Wiley, T. L., & Block, M.G. (1979). Static acoustic-immittance measurements. Journal of Speech and Hearing Research. 22. 677-696. Wiley, T. L., Oviatt, D. L., & Block, M. G. (1987). Acoustic-immittance measures in normal ears. Journal of Speech and Hearing Research, 30, 161-170. Wilson, R. H., Shanks, J. E., & Kaplan, S. K. (1984). Tympanometric changes at 226 Hz and 678 Hz across 10 trials and for two directions of ear-canal pressure change. Journal of Speech and Hearing Research, 27, 257-266. Received August 9, 1990 Accepted December 8, 1990 Requests for reprints should be sent to Terry L. Wiley, PhD, Department of Communicative Disorders, University of WisconsinMadison, 1975 Willow Drive, Madison, WI 53706.
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Test Retest Reliability in Tympanometry Terry L. Wiley Kathryn A. Barrett University of Wisconsin-Madison
Test-retest reliability for tympanometric measures was evaluated across five sessions in 20 subjects with normal hearing and normal middle-ear function. Tympanograms were obtained on each ear for probe frequencies of 226, 678, and 1000 Hz using both ascending and descending directions of pressure change. Across all conditions, the tympanometric measure that consistently demonstrated the highest test-retest reliability was compensated static acoustic admittance. Test-retest correlations for peak compensated static acoustic admittance measures were higher than those for ambient measures across all probe frequencies and both directions of pressure change; the differences in correlations for peak and ambient measures, however, reached significance only for 226-Hz conditions. Across-session correlations for tympanogram width did not differ significantly for measures referenced to the lowest tympanogram tail and those referenced to +200 daPa. KEY WORDS: tympanometry, reliability, admittance
Acoustic immittance measures are routinely used in most audiology clinics (Martin & Sides, 1985). Tympanometric measures, for example, are integral parts of the test protocol in the "Guidelines for Screening for Hearing Impairment and Middle Ear Disorders" recommended by the American Speech-Language-Hearing Association (ASHA, 1990). In spite of the diagnostic value and popularity of acoustic immittance measures in clinical applications, there are limited data available on the variability and reliability of acoustic immittance measures over repeated trials and test sessions. Knowledge of test-retest reliability for acoustic immittance measures is particularly crucial inclinical applications. The determination of a pathologic condition or the need to monitor the progress or the remediation of a pathologic condition may require several evaluations on separate days. Accordingly, specification of normal limits in test-retest variability is necessary to determine whether changes in middle-ear function reflected in acoustic immittance measures are due to normal variation or to actual changes in pathologic condition. Published data regarding the test-retest reliability of acoustic immittance measures, however, are limited both in their availability and in their application. Tillman, Dallos, and Kuruvilla (1964), Nixon and Glorig (1964), and Feldman (1967) evaluated the reliability of acoustic immittance measures for normal subjects. In these earlier studies, however, only compensated static acoustic irnmittance measures were reported, and the measures were obtained with an instrument (Zwislocki Mechano-Acoustic Bridge) that is no longer commercially available. In addition, the probe frequencies used are not available on most current instruments. Liden, Peterson, and Bjorkman (1970) provided test-retest data for tympanometry in 3 normal adults. The authors used a custom-built instrument and reported test-retest data over 20 trials in a 10-hr period for a probe-tone frequency of 800 Hz. Tympanometric variables examined included notch depth (in dB), notch width (in mm), deviation of the tympanogram peak from 0 (in mm), and the difference (in dB SPL) "between the two endpoints of the tympanogram (p. 251)." These earlier data © 1991, American Speech-Language-Hearing Association
1197
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0022-.4685/913405-1 197$0 1.00/0
1198 Journal of Speech and Heanng Research
are of limited current application because the primary data were presented in variables and units that cannot be applied to present clinical protocols and instruments, and the probe frequency of 800 Hz is not available on most currently available instruments. Feldman, Djupesland, and Grimes (1971) compared static compliance measures and compensated static acoustic impedance measures for a Zwislocki Acoustic Bridge and a Madsen (Z070) Electroacoustic Bridge, respectively. Eleven normal-hearing subjects experienced three trials for each instrument. High test-retest correlations between trials and between instruments were reported for the two sets of measures. Measures for the Madsen device were limited to compensated acoustic impedance magnitude (without associated phase angles) based on tympanometric values at ambient pressure and at +200 daPa. Such vector measures and the use of +200 daPa as a referent for ear canal contributions both result in significant error (Lilly & Shanks, 1981; Wiley & Block, 1979). Furthermore, these results reflect only on compensated static measures for a small sample of normal-hearing subjects. Porter and Winston (1973) reported reliability data for compensated static acoustic admittance measures on 16 normal-hearing subjects across five test sessions. Probe frequencies of 220 and 660 Hz were used. Acoustic susceptance was measured with pressure decreasing from +200 daPa, and acoustic conductance was measured with pressure increasing from -200 daPa. Values obtained at -200 daPa and ambient pressure or tympanometric peak pressure were used to calculate compensated static values. Means, standard deviations, and standard errors were reported for acoustic conductance and acoustic susceptance at probe frequencies of 220 and 660 Hz. Porter and Winston did not report the distribution characteristics of their static acoustic admittance data, but recent findings suggest that such data are positively skewed regardless of the referent for ear canal contributions (Wiley, Oviatt, & Block, 1987). Test-retest correlations reported by Porter and Winston were high for static measures referenced to tympanometric peak pressure. However, low test-retest correlation coefficients were reported for static measures referenced to ambient pressure, particularly for measures of acoustic conductance. Porter and Winston suggested that these low correlations reflected small shifts in the tympanometric peak pressure over time. The tympanometric peak pressure varied from test to test, although never more than 20 daPa. In addition, however, Wilson, Shanks, and Kaplan (1984) have reported increased complexity inthe configuration of tympanograms when an ascending direction of pressure change is used. The use of different directions of pressure change for obtaining acoustic conductance and acoustic susceptance tympanograms, then, also could have contributed to the increased variability in static acoustic conductance measures reported by Porter and Winston (1973). Finally, comparisons of the reliability between the two probe frequencies and the method for computation of static values for notched 660-Hz tympanograms were not presented. Reports of the test-retest reliability of acoustic immittance measures are few and are limited in clinical utility. Normal variations in most acoustic immittance measures across test
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sessions have yet to be established, particularly for more contemporary measures and instruments. Most past reports have been limited to compensated static acoustic immittance measures. Knowledge of the test-retest reliability and the limits of normal variance in acoustic immittance measures is crucial in making clinical decisions regarding the status of middle-ear function based on acoustic immittance measures. Thus, the purpose of this study was to quantify the normal test-retest reliability and variability for acoustic admittance measures across test sessions.
Method Subjects Twenty normal-hearing young adults (10 females, 10 males) between the ages of 18 and 25 years served as subjects. All subjects presented a negative history of otologic disease, particularly during adulthood. The subjects were primarily recruited from the undergraduate and graduate student population at the University of Wisconsin-Madison. All subjects had normal hearing and normal middle-ear function based on behavioral audiometry, tympanometry, and contralateral acoustic reflex measures. Normal hearing was defined as auditory thresholds equal to or less than 10 dB HL (ANSI, 1989) for tones of 500, 1000, 2000, 4000, and 8000 Hz in both ears. All subjects also presented normal acoustic admittance tympanograms, acoustic reflex thresholds for a 1000-Hz activator, and compensated static acoustic admittance values for a 226-Hz probe (Wiley et al., 1987). Test Measures All test measures were obtained in a sound-treated room (Industrial Acoustics Corporation, 1200 Series, #101539). Each subject participated in five test sessions scheduled no less than 24 hr and no more than 7 days apart. Acoustic admittance tympanograms were obtained on each ear for independent probe frequencies of 226, 678, and 1000 Hz. Both ascending (-400 daPa to 400 daPa, -/+) and descending (400 daPa to -400 daPa, +/-) directions of pressure change were used to obtain tympanograms at each probe frequency. Thus, tympanograms for the following six conditions were obtained for each ear during each of the five test sessions: 226 Hz, +/-; 226 Hz, -/+; 678 Hz, +/-; 678 Hz, -/+; 1000 Hz, +/-; and 1000 Hz, -/+. The acoustic immittance system used for obtaining the experimental measures enabled representation and analysis of tympanograms in polar (acoustic admittance and phase angle) and rectangular (acoustic conductance and acoustic susceptance) forms. The order of conditions was randomly assigned without replacement for each ear and session. The first ear tested (right or left) was randomly selected at the beginning of the initial test session and alternated for the remaining four sessions. The probe unit and tip were removed from the ear canal immediately following a set of three tympanometric trials. A rest interval of approximately 5 min preceded reinsertion of the probe tip for each ear.
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Wiley & Barrett: Test-Retest Reliabty
Instrumentation Behavioral thresholds for tones were obtained with a diagnostic audiometer (Grason-Stadler, GSI 16) calibrated in accordance with ANSI (S3.6-1989) specifications. All acoustic immittance measures were obtained using a softwaredriven acoustic immittance system (Nicolet, Aurora, Middle Ear Analyzer, Version 4.20) calibrated according to ANSI (S3.39-1987) specifications for Type I Aural Acoustic Immittance Instruments. The measured pump speed of the acoustic immittance instrument was 50 daPa/s.
Data Analysis Test-retest reliability for peak pressure, compensated static acoustic admittance measures, and tympanogram width were evaluated across test sessions for each direction of pressure change and for each probe frequency. All tympanograms were obtained in a measurement-plane mode. Compensated static acoustic admittance values were determined using peak and ambient pressure referenced to the lowest tail value and to the value at +200 daPa. Tympanogram-width measures were calculated using the value at peak pressure in reference to both the lowest tail value (Koebsell & Margolis, 1986) and the value at +200 daPa (Koebsell, Shanks, Cone-Wesson, & Wilson, 1988). Testretest reliability for each measure across sessions was evaluated using Pearson product moment correlations.
Results Tympanometric Data Averaged data across sessions for each tympanometric variable and experimental condition are shown in Table 1. Each tabled value is based on measures across five sessions, 20 subjects, and two ears (200 total measures). Based on the earlier finding (Wiley et al., 1987) that tympanometric measures are positively skewed, a nonparametric test (sign test) was performed on all variables and conditions for the right and left ears. Sign-test results indicated that only 16 out of 450 measures were significantly different for the two ears. This outcome is within a Type-I error of 5%. As a result, the data for all measures and conditions were collapsed across ears for presentations and statistical analyses. Tympanogram width is reported only for tympanograms obtained with the 226-Hz probe. At higher probe frequencies, tympanogram notching occurred for different subjects within the group and the presence of notching substantially altered tympanogram-width estimates for these subjects. Further, reported norms and clinical applications of tympanogramwidth measures presently are limited to measures for a 226-Hz probe frequency (ASHA, 1990). Session-to-session variability. In addition to measures of central tendency across sessions for each variable, Table 1 includes the 90% range of values across sessions, the mean difference across sessions, and a ratio of the variance to the mean (90% range/mean). The range was used as a measure of dispersion given past work (Wiley et al., 1987)
1199
demonstrating skewed distributions for the variables of interest. The 90% range/mean ratios are provided as a means of evaluating differences in variance for test variables with different units and dimensions of measure. Also, this measure (90% range/mean ratio) enables, comparison of sessionto-session variability and test-retest reliability for measures that have similar ratios. The variability across sessions differed considerably for variables and for probe frequency. Across-probe frequencies and directions of pressure change, acoustic conductance, and acoustic admittance measures evidenced the least variability and the lowest and most stable 90% range/mean ratios. Only acoustic conductance, acoustic admittance, and peak pressure offered similar 90% range/mean ratios across the two directions of pressure change and across the three probe frequencies. Other measures, particularly acoustic susceptance and phase angle measures, demonstrated increased variability and higher 900/c range/mean ratios at higher probe frequencies. In general, peak measures evidenced less session-tosession variability and lower 90% range/mean ratios relative to ambient, compensated measures. This was particularly evident for 678-Hz and 1000-Hz probe frequencies. Finally, across all variables, session-to-session variability and 90% range/mean ratios were least for a 226-Hz probe relative to higher probe frequencies. Tympanogram notching. The complexity of tympanometric patterns increased with increased probe frequency (Table 2). Only single-peaked tympanograms were observed at a probe frequency of 226 Hz; notched tympanograms were observed in a substantial number of cases for 678- and 1000-Hz probes. This likely accounts for the increased session-to-session variability observed at the higher probe frequencies (Table 1). In contrast to Wilson et al. (1984), who reported a greater number of notched tympanograms at a probe frequency of 678 Hz for a negative-to-positive (-/+) direction of pressure change than for a positive-to-negative (+/-) direction, little difference in the number of notched tympanograms for the two directions of pressure change using a 678-Hz probe was noted in the present study. At a probe frequency of 1000 Hz, we did observe a greater number of notched tympanograms for the -/+ direction of pressure change than for the +/- direction. The session-to-session variation in tympanogram pattems for 678-Hz and 1000-Hz probe frequencies is summarized in Table 3. The tympanogram types or shapes are those of Vanhuyse, Creten, and Van Camp ('1975) for acoustic conductance and acoustic susceptance tympanograms. The total for each tympanogram type was relatively stable across the five sessions. The session totals, however, do not reflect the shifts in tympanogram patterns for individual subjects across sessions. These shifts influence test-retest reliability and session-to-session variability. A tabulation of session-tosession shifts in tympanogram category is provided in Table 4. Most shifts from one pattern to another across the five sessions were limited to one category. Specifically, sessionto-session pattern shifts across both 678-Hz and 1000-Hz probes for both directions of pressure change were -+1 category in 85% of the cases. A shift in excess of two categories was observed in only one case. For both probe
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1200 Journalof Speech and Hearing Research
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TABLE 1. Means (M), medians, mean differences (M DIFF), 900% ranges and 90% range/M ratios across sessions and ears for measures obtained under conditions of probe-frequency and direction-of-pressure change.
Variable
M
Ambient Ga Peak Ga Ambient Ba Peak B Ambient Ya Peak Ya Ambient Ya (+200) Peak Y, (+200) Ambient y Peak 4by Ambient by, (+200) Peak by (+200) Tympanogram width Tympanogram width (+200) Peak pressure
.30 .34 .58 .76 .66 .84 .51 .69 62 66 58 64 103 79 23
Ambient Ga Peak Ga Ambient Ba Peak Ba Ambient Ya Peak Ya Ambient Ya (+200) Peak Ya (+200) Ambient by Peak ,by Ambient by (+2 0 0) Peak by (+200) Peak pressure
1.55 2.11 .15 .80 1.72 2.37 1.66 2.15 10 20 -13 5 27
Ambient Ga Peak Ga Ambient Ba Peak Ba Ambient Ya Peak Ya Ambient Ya (+200) Peak Y, (+200) Ambient by Peak y Ambient (by (+200) Peak by (+200) Peak pressure
2.29 3.00 -. 09
1.35 2.67 3.85 2.97 3.10 5.00 24.0 -32 0 47
Median
M DIFF
90%/o
90% R
Condition: 226-Hz Negative-to-positive .28 .003 .10-.53 .29 .005 .12-.62 .51 .009 .29-1.14 .68 .010 .38-1.39 .61 .009 .32-1.23 .77 .006 .43-1.48 .46 .009 .21-1.02 .61 .007 .34-1.28 63 .06 46-79 67 .46 51-81 57 .06 41-80 64 .57 47-83 105 .28 60-145 80 25
.81 1.16
45-110 -5-45
R/M
M
1.43 1.47 1.47 1.33 1.38 1.25 1.59 1.36 0.53 0.45 0.67 0.56 0.83
69 69 64 63 110
0.82 2.17
80 -13
Condition: 678-Hz Negative-to-positive 1.35 .047 .70-2.84 1.38 1.94 .006 1.01-3.61 1.23 .27 .022 -1.26-1.38 17.6 .71 .041 -. 24-2.44 3.35 1.44 .051 .82-3.26 1.42 2.09 .008 1.16-4.05 1.22 1.41 .066 .76-3.32 1.54 1.9 .001 1.07-3.86 1.30 11 .34 -36-44 8.00 22 .02 -70-45 5.75 -10 .34 -48-24 5.54 5 .57 -23-3 11.60 30 .91 -5-45 1 85 Condition: 1000-Hz Negative-to-positive 2.36 .04 0-4.25 1.86 3.05 .06 .65-5.33 1.56 .03 .06 -. 24-2.0 24.89 1.02 .12 -.83-5.34 4.57 2.50 .02 .93-5.02 1.53 3.80 .07 1.84-6.74 1.27 2.61 .01 1.1-5.79 1.58 3.12 .06 .86-5.3 1.43 1.00 2.01 -37-75 22.40 21.0 1.38 -11-80 3.79 -32 .29 --70-3 2.28 0 .06 -34-28 45 1.00 10-105 2.02
.26 .31 .70 .79 .75 .86 .61 .72
1.97 2.25 .41 .36 2.12 2.38 1.86 2.14 13 10 2 --3 -13 2.87 3.25 .07 .76 3.18 3.70 3.35 3.38 7 17
-16 -4 9
Median
M DIFF
90%o
90% R
Condition: 226-Hz Positive-to-negative .25 .004 .05-.54 .29 .004 .11-.57 .64 .011 .34-1.25 .74 .014 .43-1.3 .70 .009 .38-1.32 .80 .012 .45-1.38 .56 .007 .26-1.06 .68 .009 .36-1.16 71 .75 54-84 70 .69 54-80 64 .92 45-77 63 .75 46-77 108 1.06 70-155 80 -5
.03 1.09
55-110 -40-5
R/M 1.88 1.48 1.30 1.10
1.25 1.08 1.31 111
0.43 0.38 0.50 0.49 0.77 0.69 -3.46
Condition: 678-Hz Positive-to-negative 1.85 .018 .89-3.33 2.11 .019 1.17-3.67 .42 .023 -.54-1.52 .34 .033 -.90-1.64 1.98 .020 1.12-3.40 2.28 .009 1.30-3.90 1.75 .013 .89-3.17 198 .014 1.16-3.58 12 .40 -21-44 9 .97 -17-37 -1 .17 -32-27 -23 .75 -30-25 -5 1.16 -40-5
1.24 1.11 5.02 7.06 1.08 1.09 1.23 1.13 5.00 5.40 29.50 18.33 3.46
Condition: 1000-Hz Positive-to-negative 2.91 .066 .19-4.86 3.44 .057 .51-5.58 .33 .03 -2.63-1.69 .78 .06 -1.23-3.92 3.21 .066 1.03-5.10 3.69 .03 2.03-5.60 3.54 .02 1.23-5.40 3.39 .01 1.28-5.75 6 1.01 -35-54 14 1.38 -14-76 -13 .17 -54-17 -3 1.66 -29-21 5 .06 -45-65
1.63 1.56 61.71 6.78 1.28 0.96 1.24 1.32 12.71 5.29 4.44 12.50 12.20
Note. All values for Ga, Ba,,Y and 4y, are compensated static measures. The values for Ga, Ba, and Ya are in mmhos, values for by are in degrees, and values for tympanogram width and peak pressure are in daPa. Each tabled value is based on 200 measures (5 sessions/2 ears/20 subjects). Tympanogram-width measures are provided only for the 226-Hz probe conditions. Mean differences are the mean of mean differences across the five sessions for each variable. frequencies, the number of shifts for a positive-to-negative direction of pressure change was greater than that for a negative-to-positive direction.
Test-Retest Reliability Test-retest correlations for each probe frequency are shown in Table 5. Mean correlations for each ear, direction of pressure change, and tympanometric variable between sessions are provided. The grand mean in each table represents the mean of mean correlations across right and left ears. The
90% range refers to the upper (95%) and lower (5%) limit of correlations across both ears. Pressure direction.Mean correlations for each ear, grand mean correlation values, and the ranges of correlations suggested similar test-retest reliability for the two directions of pressure change for each probe frequency. The mean difference in correlations across all tympanometric variables and across the two directions of pressure change were 0.06 for 226 Hz, 0.12 for 678 Hz, and 0.08 for 1000 Hz. Ambient versus peak measures. Test-retest reliability, as reflected in session-to-session correlations, was similar
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Wiley & Barrett: Te:st-Retest Reliabhlity
1201
TABLE 2. Number and percentage of tympanogram patterns for each condition across ears. Numbers and percentages for each probe frequency and direction of pressure change (+/and -/+) and the grand totals and percentages are displayed. The classification of tympanogram patterns Is that reported by Vanhuyse, Cretan, and Van Camp (1975). Shape/Condition
1B1G
226 Hz 226 +/226-/+ Total Percent 678 Hz 678 +/678 -/+ Total Percent 1000 Hz 1000 +/1000 -/+ Total Percent Total Percent
3B1 G
3B3G
5B3G
Other
Total
0 0 0 0%
200 200 400
200 200 400 100%
0 0 0 0%
0 0 0 0%
0 0 0 0%
42 49 91 23%
145 140 285 71%
4 4 8 2%
7 6 13 3%
2 1 3 1%
200 200 400
22 2 24 6%
163 167 330 83%
14 28 42 11%
1 1 2 < 1%
0 0 0 0%
200 198 398
515 43%
615 51%
50 4%
15 1%
3 .05] or positive-to-negative [t(17) = 0.49, p > .05] direction of pressure change. Probe frequency. As is evident from Figure 1, test-retest reliability varied across probe frequency for all compensated static measures. Peak compensated static acoustic admittance measures demonstrated good test-retest reliability across all three probe frequencies. The reliability of acoustic conductance and acoustic susceptance measures, however, varied considerTABLE 4. Shifts In tympanogram categories for each condition (probe frequency and direction of pressure change) across the five sessions and across the 40 ears. Number of shifts Shifts in category
678 Hz -/+
678 Hz +/-
1000 Hz -/+
1000 Hz +/-
+3 +2 +1 -1 -2
0 2 14 15 2
0 6 16 13 5
0 0 10 8 0
1 0 13 15 2
Note. The entries for shifts represent the number of positive or negative category shifts from session to session. A positive shift indicates increased tympanogram notching, and a negative shift indicates a shift to a tympanogram category with less notching.
TABLE 3. Number of each tympanogram pattern (shape) across sessions for 678-Hz and 1000-Hz probes and for both directions (-/+ and +/-) of pressure change. The tympanogram shape categories are those of Vanhuyse, Cretan, and Van Camp (1975). 678 Hz -/+ Session
678 Hz +Session
1000 Hz -/+ Session
1000 Hz +/Session
Shape
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1B1G 3B1 G 3B3G 5B3G Other Total
8 30 1 1 0 40
11 26 3 0 0 40
10 27 0 2 1 40
13 26 0 1 0 40
8 30 0 2 0 40
8 30 1 1 0 40
9 29 0 1 1 40
8 28 1 2 1 40
10 29 1 0 0 40
7 29 1 3 0 40
0 38 2 0 0 40
1 33 6 0 0 40
0 33 6 0 1 40
1 30 8 1 0 40
0 34 6 0 0 40
2 36 2 0 0 40
7 28 5 0 0 40
6 30 4 0 0 40
3 35 1 1 0 40
5 33 2 0 0 40
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1202
Jourmal of Speech and Heanng Research
34
1197-1206 October 1991
TABLE 5. Mean correlations for both right and left ears, correlation grand means and correlation ranges across five sessions for measures obtained under conditions of probe-frequency and direction-of-pressure change.
Variable Ambient Ga Peak Ga Ambient Ba Peak Ba Ambient Y, Peak Ya Ambient Y. (+200) Peak Y (+200) Ambient $y Peak y Ambient $y (+200) Peak y,(+200) Tympanogram width Tympanogram width (+200) Peak pressure Ambient Ga Peak Ga Ambient Ba Peak Ba Ambient Ya Peak Y Ambient Ya (+200) Peak Y, (+200) Ambient 1y Peak 0y Ambient (4y(+200) Peak $y(+200) Peak pressure Ambient Ga Peak Ga Ambient Ba Peak Ba Ambient Ya Peak Ya Ambient Ya (+200) Peak Ya (+200) Ambient Iy Peak y Ambient y, (+200) Peak 4y (+200) Peak pressure
Right
Left
Grand Mean
Range
Right
Left
Grand Mean
Range
Condition: 226-Hz Negative-to-positive .52 .38 .45 .14-.64 .42 .39 .41 .20-.55
.68 .53
.73 .90
.65 .86
.69 .88
.17-.91 .77-.93
.83 .85
.74 .81
.79 .83
.74 .88
.63 .83
.68 .86
.12-.91 .72-.91
.83
.72
.78
58-.90
.83
.80
.82
.68-.93
.69
.63
.66
.09-.90
.90 .49 .44 .38 .46 .72 .54
.86 .38 .42 .24 .41 .56 .48
.88 .43 .43 .31 .44 .64 .51
.79-.92 .16-.61 .30-.60 .10-.54 .22-.62 .25-.84 .24-.72
.83 .86 .62 .57 .54
.71 .79 .30 .36 .30
.77 .83 .46 .47 .42
.57-.89 .67-.92 .23-.73 .28-.67 .09-.72
.55
.41
.48
.18-.69
.69
.46
.58
.43-.80
.70 .68 .65
.62 .47 .29
.66 .58 .47
.45-.86 .39-.79 - 33-.75
Condition: 678-Hz Negative-to-positive .68 .66 .67 .53-.78 .46 .80 .63 .12-.90 .39 .74 .57 -.16-.88 .12 .61 .37 -. 10-.92 .71 .71 .71 .57-.85 .51 .87 .69 .12-.93 .60 .71 .66 .33-.81 .47 .77 .62 .07-.91 .50 .81 .61 .15-.90 .30 .60 .45 -. 03-.91 .45 .78 .62 .03-.88 .31 .69 .50 .03-.89 .50 .54 .52 .04-.83 Condition: 1000-Hz Negative-to-positive .29 .75 .52 -. 18-.94 .34 .84 .59 -.18-.90 .19 .25 .35 .64 .43 .56 .31 .18 .31 .37 .32
.38 .67 .57 .86 .68 .81 .45 .72 .73 .39 .90
.29 .46 .46 .75 .56 .69 .38 .45 .52 .38 .61
-. 11-.69 -. 29-.82 - .05-.79 .42-.93 .02-.78 .34-.90 - .05-.81 -. 37-.85 - .30-.92 .05-.83 -. 16-.94
.83 .83 .67 .63 .86 .87 .81 .83 .79 .71
Condition: 226-Hz Positive-to-negative .38 .54 .16-.73 .43 .48 .22-.61 .57-.90 .69-.93
Condition: 678-Hz Positive-to-negative .79 .81 .65-.91 .80 .82 .74-.92 .29 .48 .07-.81 .32 .48 .11-.78 .85 .86 .68-.91 .87 .87 .82-.94 .72 .77 .54-.87 .78 .81 .68-.88 .59 .69 .44-.90 .55 .63 .36-.82
.74
.60
.67
.50-.90
.66 .70
.56 .67
.61 .69
.34-.78 .59-.74
Condition: 1000-Hz Positive-to-negative .45 .62 .49
.48 .44
.80 .79
.74 .40 .42 .79 .44 .81
.52
.49
-. 10-.84
.63 .53 .55 .50 .58 .39 .45 .49 .65 .63
.63 .51 .52 .47 .69 .59 .60 .45 .54 .71
-. 15-.89 -.07-.91 --.06-.85 .01-.82 -.07-.91 .02-.90 - .26-.85 -.08-.85 -.07-.89 .02-.93
.57
.51
.17-.80
.50
.66
- .28-.92
Note. Correlations for each ear are based on 100 measures (5 sessions/20 subjects). The grand mean correlation is the mean of mean correlations for the five sessions and is based on 200 measures (5 sessions/20 subjects/2 ears); the range is based on both right and left ear correlations across five sessions. ably across probe frequencies. Comparatively, for example, acoustic conductance measures demonstrated higher reliability at 678 Hz for both ambient (r = .74) and peak (r = .73) conditions than did corresponding measures of acoustic susceptance (ambient r = .53, peak r = .43). Acoustic susceptance measures, however, evidenced higher test-retest reliability at 226 Hz for ambient (r = .74) and peak (r = .86) conditions relative to acoustic conductance measures (ambient r = .50, peak r = .45). Like acoustic admittance measures, component measures referenced to the tympanometric peak typically were superior in reliability to ambient measures. Test-retest reliability for admittance phase angle also varied across probe frequency; peak measures of admittance phase angle evidenced more stable
test-retest reliability across probe frequency relative to ambient phase angle measures.
Discussion ------The primary purpose of the present study was to evaluate the session-to-session reliability for tympanometric measures used in clinical practice. Reports on such test-retest reliability have been few and, further, have been limited in application with respect to present clinical protocols. As was noted in the introduction, it is not feasible or appropriate to compare data from most of the earlier studies with data
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Wiley & Barrett: Test-Retest Reliability
a
1.0
10
08
0.8
1203
e 0.6
0.6
z < 0.4
m 0.4
02
02
o P1000 [] P678 * P226
00 G
B
Y
O P1000 1 P678 * P226
00 Y
PH
Y2
PH
PH2
TW
TW2
MEASURE
MEASURE 1.0
10
0.8
0.8
a 0.6
.o 06
Z 04
Z 04
D
02
02
o
oCP1000
P1000 El P678 * P226
[] P678 0.0
* P226 G
B
Y
0.0 Y
PH
obtained from current instrumentation such as that used in the present study. A limited exception is the work of Porter and Winston (1973). Porter and Winston reported test-retest correlations for compensated static acoustic conductance and acoustic susceptance measures across five sessions in 16 "normal-hearing" subjects "with presumably normal middle ears" (p. 142). Data referenced to both peak and ambient pressures were provided. Figure 3 shows mean correlations from the Porter and Winston work and corresponding correlations from the present study. In conformity with the procedures used by Porter and Winston, acoustic conductance data in Figure 3 for the present study are limited to mean correlations for the negative-to-positive direction of pressure
PH
PH2
TW
TW2
MEASURE
MEASURE
FIGURE 1. Grand mean correlations (across the five sessions) for peak (top panel) and ambient (lower panel) compensated static measures at probe frequencies of 226 (P226), 678 (P678), and 1000 (P1000) Hz. All compensated values are referenced to the lowest tall of the tympanograms. Correlations are based on acoustic conductance (G), acoustic susceptance (B), acoustic admittance (Y), and admittance phase angle (PH) measures averaged across both ears and both directions of pressure change.
Y2
FIGURE 2. Grand mean correlations (across the five sessions) for peak (top panel) and ambient (lower panel) compensated static acoustic admittance (Y)and admittance phase angle (PH) at probe frequencies of 226 (P226), 678 (P678), and 1000 (P1000) Hz. Variables associated with the descriptor 2 were based on ear canal corrections referenced to +200 daPa, and all others were based on the lowest tympanogram tail. Tympanogram-
width (TW) measures, limited to the single probe frequency of 226 Hz, also are Included. Correlations are based on means for each measure across both ears and both directions of pressure change. change, and data for acoustic susceptance are for the positive-to-negative direction of pressure change. Also, Porter and Winston used 220- and 660.-Hz probe frequencies; comparable data from the present study are based on probe frequencies of 226 and 678 Hz. Clearly, as Figure 3 illustrates, there are substantial differences in reported test-retest reliability for the two studies. With the exception of ambient compensated static acoustic conductance measures at 226 (or 220) Hz, reliability correlations for the present study are lower than those reported by Porter and Winston. Also, the substantial differences in test-retest reliability for peak and
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1204
Journal of Speech and Heanng Research
1.0
0.8
>
0.6
Z 0.4
Z 0.2
0.0 GA
GP
BA
BP
MEASURE 1.0
_ 0.6
Z 0.2
0.0 GA
GP
BA
BP
MEASURE
FIGURE 3. Correlations for peak (P) and ambient (A) compensated static acoustic conductance (G) and acoustic susceptance (B) from Porter and Winston (1973) and from the present study. For both sets of data, acoustic conductance measures were obtained using a negative-to-positive direction of pressure change, and acoustic susceptance measures were obtained with a positive-to-negative direction of pressure change. The Porter and Winston data are mean correlations for probe frequencies of 220 (PW 220) and 660 (PW 660) Hz. Data for the present study are grand mean correlations (across the five sessions) at probe frequencies of 226 (WB 226) and 678 (WB 678) Hz. Correlations for the present study were based on compensated values referenced to the lowest tail of tympanograms. ambient measures reported by Porter and Winston were not observed in the present study. The disparity in test-retest reliability across the two studies is most apparent at the higher probe frequency (660 or 678 Hz). This may be due, in part, to differences in data analyses for notched tympanograms. In the present study, notched tympanograms were observed in a substantial number of cases for 678- and 1000-Hz probes (Table 2). Indeed, tympanogram notching and shifts in tympanogram categories across session (Tables 3 and 4) likely contributed heavily to the reduced test-retest reliability for acoustic admittance components
34
1197-1206
ctober 1991
(acoustic conductance, acoustic susceptance, acoustic admittance, admittance phase angle) at higher probe frequencies approximating the resonance frequency of the middleear transmission system. As expected, this effect was most dramatic for the reactive component (acoustic susceptance). Porter and Winston did not report whether notched tympanograms were observed in their subject group for the 660-Hz probe, nor did they report the calculation method for deriving compensated static values in such cases. If Porter and Winston excluded cases of notched tympanograms or if they did not use the notch as a basis for compensated calculations, less variability across sessions might have resulted. Regardless of the specific source(s) for differences in the two studies, our present results are not consistent with the high test-retest reliability in acoustic admittance components or the substantial superiority in test-retest reliability for compensated peak measures relative to ambient measures originally reported by Porter and Winston. In the present study, correlations for peak compensated measures typically were higher than those for ambient measures. However, our test-retest correlations were generally lower and the differences in peak and ambient correlations were generally much smaller than those reported by Porter and Winston. Across all conditions (probe frequency, ear, direction of pressure, and ear canal reference), the tympanometric measure that consistently demonstrated the highest test-retest reliability in the present study was compensated static acoustic admittance. Peak compensated acoustic admittance measures were superior to ambient measures in terms of session-to-session variability (Table 1) and in terms of test-retest reliability (Table 5). Two-tailed tests of significance on dependent correlations (Bruning & Kintz, 1977, pp. 215-217) were performed on the correlations (Table 5) for compensated static peak and ambient acoustic admittance referenced to both the lowest tympanometric tail and +200 daPa for all three probe frequencies. Significant dependent correlations were obtained only for the 226-Hz probe using a negative-to-positive direction of pressure change. Acrosssession correlations for peak static measures were significantly different from those for ambient measures in the case of both +200 daPa [t (17) = 2.92, p < .05] and lowest tail [t (17) = 2.51, p < .05] ear canal referents. In all cases, test-retest correlations for peak measures were higher than those for ambient measures. Peak compensated static acoustic admittance and tympanogram width are primary acoustic immittance measures recommended by the American Speech-Language-Hearing Association (1990) for screening of middle-ear function. If acoustic admittance measures are restricted to a low-frequency probe (226 Hz), as in the ASHA guidelines for screening, these two measures offer different degrees of test-retest reliability according to the present study. A summary of mean across-session correlations for basic tympanometric measures at 226 Hz from the present study is provided in Figure 4. Correlations for peak compensated static acoustic susceptance and acoustic admittance are high, indicating very good test-retest reliability. Here, only peak data are provided on the basis of the analysis demonstrating higher test-retest reliability for peak measures relative to ambient measures. The close agreement in test-retest
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Wiley & Barrett: Tes:-Retest Rehability
reliability for acoustic susceptance and acoustic admittance measures is not surprising for a 226-Hz probe frequency; at low probe frequencies the middle-ear transmission system is stiffness-controlled for normal subjects. Test-retest reliability for tympanogram-width measures, using either lowest tail or +200-daPa referents, is lower than that for compensated static acoustic admittance measures. Peak pressure, admittance phase angle, and acoustic conductance measures evidence even lower test-retest reliability than that observed for tympanogram width. Finally, it should be understood that the lower overall test-retest reliability observed for acoustic conductance, acoustic susceptance, and admittance phase angle does not necessarily indicate that these particular measures are without diagnostic significance. Complex interactions between
these components, such as those that occur at frequencies approaching resonance for the middle-ear transmission system, may result in decreased session-to-session reliability. Within a session for a given subject and across sessions for a given subject, however, the characteristics and frequency loci of the interactions may be quite useful in diagnostic applications. Differences in middle-ear resonance for a subject relative to normative data and shifts in middle-ear resonance over time, for example, may be useful diagnostic indices. Similarly, the lower test-retest reliability for tympanogram-width measures may actually underlie sensitivity of the measure to changes in tympanogram characteristics associated with subtle changes in middle-ear mechanics. These changes, in turn, may be useful in diagnostic applications and in monitoring middle-ear function.
.4
1.0
0.8
0-0
0.6
Pq1
Z
0.4
W
0.2
[] P200 LT
0.0 G
B
Y
1205
PH TW PPR
MEASURE (226 Hz) FIGURE 4. Grand mean correlations (across the five sessions) for acoustic conductance (G), acoustic susceptance (B), acoustic admittance (Y), admittance phase angle (PH), tympanogram width (TW) and peak tympanogram pressure (PPR) at a probe frequency of 226 Hz. All acoustic admittance measures (G,B,Y, PH) are peak compensated static means across both directions of pressure change. The filled bars represent ear canal corrections referenced to the lowest tympanogram tail; hatched bars represent ear canal corrections referenced to +200 daPa.
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1206
Journal of Speech and Heanng Research
Acknowledgments The authors wish to thank Dee K. Vetter for her advice regarding statistical analyses, Scott Rose for necessary software development, and Nicolet Instrument Corporation, Madison, WI, for the use of the Aurora system used in data collection. A paper based on portions of this research was presented at the 1989 Annual Convention of the American Speech-Language-Hearing Association in St. Louis, Mo.
References American National Standards Institute. (1987). American National Standard specifications for instruments to measure aural acoustic impedance and admittance (aural acoustic immittance) (ANSI S3.39-1987). New York: ANSI. American National Standards Institute. (1989). American National Standard specification for audiometers (ANSI S3.6-1989). New York: ANSI. American Speech-Language-Hearing Association (ASHA). (1990). Guidelines for screening for hearing impairment and middle ear disorders. Asha, 32(Suppl. 2), 17-24. Bruning, J. L., & Klntz, B. L. (1977). Computational handbook of statistics (2nd ed.). Glenview, IL: Scott, Foresman Feldman, A. (1967). Acoustic impedance studies of the normal ear. Journal of Speech and Hearing Research, 10, 165-176. Feldman, A., Djupesland, G., & Grimes, C. T. (1971). A comparison of impedance measurements with mechanical and electroacoustic impedance measuring devices. Archives of Otolaryngology, 93, 416-418. Koebsell, K. A., & Margolis, R. H. (1986). Tympanometric gradient measured from normal preschool children. Audiology, 25, 149157. Koebsell, K. A., Shanks, J. E., Cone-Wesson, B. K., & Wilson, R. H. (1988). Tympanometric width measures in normal and pathologic ears. Asha, 30, 99 (Abstract No. 10).
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October 1991
Liden, G., Peterson, J. L., & Bjorkman, G. (1970). Tympanometry. Archives of Otolaryngology, 92, 248-257. Lilly, D.J., & Shanks, J. E. (1981). Acoustic immittance of an enclosed volume of air. In G. Popelka (Ed.), Hearing assessment with the acoustic reflex (App. B, pp. 145-160). New York: Grune & Stratton. Martin, F. N., & Sides, D. G. (1985). Survey of current audiometric practices. Asha, 27, 29-36. Nixon, J. C., & Glorig, A. (1964). Reliability of acoustic impedance measurements of the eardrum. Journal of Auditory Research, 4, 261-276. Porter, T. A., & Winston, M. E. (1973). Reliability of measures obtained with the otoadmittance meter. Journal of Auditory Research, 13, 142-146. Tillman, T. W., Dallos, P. J., & Kuruvilla, I. (1964). Reliability of measures obtained with the Zwislocki acoustic bridge. Journal of the Acoustical Society of America, 36, 582-588. Vanhuyse, V. J., Creten, W. L., & Van Camp, K. J. (1975). On the W-notching of tympanograms. Scandinavian Audiology, 4, 45-50. Wiley, T. L., & Block, M.G. (1979). Static acoustic-immittance measurements. Journal of Speech and Hearing Research. 22. 677-696. Wiley, T. L., Oviatt, D. L., & Block, M. G. (1987). Acoustic-immittance measures in normal ears. Journal of Speech and Hearing Research, 30, 161-170. Wilson, R. H., Shanks, J. E., & Kaplan, S. K. (1984). Tympanometric changes at 226 Hz and 678 Hz across 10 trials and for two directions of ear-canal pressure change. Journal of Speech and Hearing Research, 27, 257-266. Received August 9, 1990 Accepted December 8, 1990 Requests for reprints should be sent to Terry L. Wiley, PhD, Department of Communicative Disorders, University of WisconsinMadison, 1975 Willow Drive, Madison, WI 53706.
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