burns 41 (2015) 990–997
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/locate/burns
The Brief Fatigue Inventory is reliable and valid for the burn patient cohort Christopher Toh a,b, Marie Li a,b, Vidya Finlay c, Teresa Jackson c, Sally Burrows b,d, Fiona M. Wood a,c,e, Dale W. Edgar a,c,f,* a
Burn Service of WA, Royal Perth Hospital, WA, Australia School of Medicine and Pharmacology, University of Western Australia, Australia c Fiona Wood Foundation, Perth, WA, Australia d Perkins Medical Research Institute, Perth, WA, Australia e Burn Injury Research Unit, University of Western Australia, Australia f Burn Injury Research Node, Institute of Health and Rehabilitation Research, University of Notre Dame, Fremantle, WA, Australia b
article info
abstract
Article history:
Objective: After burn, patients are at risk of fatigue which may influence negatively their
Received 18 September 2014
capacity to participate in activity, rehabilitation and other treatments. Fatigue may stem
Received in revised form
from the wound healing and systemic responses to burn which drive a hypermetabolic state
16 November 2014
that may persist for months. However, an established method is not available for objectively
Accepted 19 November 2014
measuring fatigue after burns. The Brief Fatigue Inventory (BFI) was hypothesised to be an appropriate option for assessments following severe burn. The primary aim of the study was to establish if the BFI was reliable and valid in a burn patient sample.
Keywords:
Methods: Adult patients admitted between 2009 and 2013 to Royal Perth Hospital Burn
Acute burns
Center were included. Patients completed the BFI and Burns Specific Health Scale Brief
Fatigue
(BSHS-B) in tandem at one, three, six and 12 months after burn. Reliability was assessed
Quality of life
using Cronbach’s alpha; construct validity using factor analysis and multi-variable regres-
Participant response outcome
sion of BFI; and, criterion validity with longitudinal regression of BFI with BSHS-B. Results: The sample (n = 587) had a median TBSA of 3% (range = 0.90). The factor analysis confirmed a single-domain construct, centred around the first scale item. Good correlation between BFI and BSHS-B scores ( p < 0.001) on longitudinal analysis confirmed criterion validity. There was a significant difference in fatigue scores between minor and major burn patients and a significant association of fatigue levels over time with TBSA. Conclusion: The BFI is a reliable and valid tool for fatigue measurement in patients during the first 12 months after burn. # 2014 Elsevier Ltd and ISBI. All rights reserved.
* Corresponding author at: Burn Service of WA, Royal Perth Hospital, WA, Australia. Tel.: +61 8 9224 3566; fax: +61 8 9224 3577. E-mail address: [email protected] (D.W. Edgar). http://dx.doi.org/10.1016/j.burns.2014.11.014 0305-4179/# 2014 Elsevier Ltd and ISBI. All rights reserved.
burns 41 (2015) 990–997
1.
Introduction
Fatigue is a distressing symptom reported by patients suffering from a wide range of medical conditions [1,2]. It is a symptom that patients with burns commonly experience [3], possibly due to the hypermetabolic response that occurs after injury [4]. The response is exacerbated by impairments in muscle and physical function, which further contribute to higher fatigue levels [4]. In larger injuries, increased cardiac work, raised body temperature and futile substrate cycling also make fatigue a more likely symptom [4,5]. In addition, the hypermetabolic changes persist long after the initial burn [4,5]. Despite the obvious precursors to fatigue in burn patients and evidence that fatigue significantly influences vitality and quality of life (QoL), it is rarely assessed by clinicians [1,2,6]. That said, to date, an instrument for measuring fatigue has not been proposed or assessed for its use after burn. The Brief Fatigue Inventory (BFI) is one such self-report tool developed originally to measure fatigue levels in cancer patients [7]. Its utility is confirmed in other conditions such as stroke and rheumatoid arthritis [8,9]. It is shorter and easier to understand than other fatigue assessment tools available [7]. The primary aim of this study was to determine if the BFI is a reliable and valid longitudinal measure of fatigue levels in a burn patient cohort. In addition, as part of the validity assessment, the study was designed to quantify the BFI performance in measuring differences between minor and major burns, in order to inform clinical recommendations for the BFI’s use by clinicians and researchers.
2.
Methods
The specific hypotheses included: (a) the internal reliability (Cronbach’s alpha) of BFI is 0.9, (b) The BFI has a significant relationship with the Burn Specific Health Scale-Brief over time (criterion validity), (c) the construct validity of the scale items is confirmable by factor analysis and (d) the BFI shows a difference in fatigue levels between minor and major (>15% TBSA) burns (sensitivity and construct validity).
2.1.
Study design and data collection
This study was a statistical assessment of the performance of the BFI in a single-centre cohort of adult burn patients. This was achieved through analysis of retrospective data, prospectively collected from patients treated for burns treated at Royal Perth Hospital (RPH), between November 2009 and July 2013. Patients were included, irrespective of possible effect modifiers, such as age, gender and mode or severity of injury. Patients were excluded if they were unable to complete the questionnaires due to intellectual capacity or if an appropriate interpreter was unavailable, as all surveys were provided in written English. The cohort included both inpatients and ambulatory patients, thus examined a broad spectrum of injury severity. The BFI and the Burn Specific Health Scale Brief (BSHS-B) questionnaires were collected in tandem in person if and when the patient attended the hospital, or by mail, at one, three, six and 12 months after burn.
2.2.
991
Brief Fatigue Inventory (BFI)
The BFI has nine (9) questions scored on a 0–10 point numeric scale such that the maximum possible fatigue (summation) score is 90 (Appendix I). The survey is presented as two parts, with the first three questions rating current, usual and worst levels of fatigue over the past 24 h. The remaining six questions request a rating of the impact of fatigue on: activity, mood, walking, work, relationships and enjoyment of life. A global BFI score may be calculated by taking the mean of the nine questions, with a higher score indicating a greater level of fatigue. In that, the maximum possible global fatigue level reportable on the scale is 10. The BFI was chosen over other instruments to minimise patient burden and as the questions are in simple language. Instruments such as the Functional Assessment of Cancer Therapy–Fatigue (FACT–F) (47 items) and the Multidimensional Fatigue Inventory (58 items) are much longer than the BFI [10,11]. The Pearson–Byars Fatigue Feeling Checklist uses more colloquial expressions like ‘‘fairly well pooped’’ and ‘‘very lively’’ [12] which are more difficult to translate for nonEnglish speaking respondents. The simple expressions used in the BFI may also be the reason that it is popularly chosen for validation in a number of other languages [13–20]. In addition, despite being concise, the BFI still correlates well with other well-established instruments such as the FACT–F and the Profile of Mood States Fatigue subscale [10,21].
2.3.
Burns specific health scale-brief
The BSHS-B is a 40-item disease specific questionnaire widely used to assess QoL outcomes after a burn [22]. This version was modified from the original BSHS, which consisted of 114 questions [23] but was shown to be equally sensitive [24]. BSHS-B has excellent internal consistency indicating the high level of reliability of the tool, which was confirmed for major and recently, minor burns [24,25]. With time after burn the BSHS-B score is expected to increase indicating recovery and improvement of quality of life.
2.4.
Statistical methods
Statistical analyses were conducted using STATA (v.12 Statacorp, Texas). Descriptive statistics of patient demographics were presented as median, upper and lower quartiles of the inter-quartile range (Q1–Q3) where the variables are continuous, or as percentages where they are categorical. Variables which were identified as possible factors that influence fatigue levels in burns, trauma and other patient populations were examined as covariates in all multivariable models. These included: time since injury, age, gender, injury severity markers and their interaction terms. The severity markers included total burn surface area [TBSA] and category of burn (where major burn was defined as >15% TBSA).
2.4.1.
Reliability
The BFI survey was assessed for internal consistency, as a measure of reliability, using Cronbach’s alpha calculated from all available responses. The greater the value of alpha, the
992
burns 41 (2015) 990–997
greater its internal consistency [26]. Bland and Altman (1997) recommended an alpha 0.9 is desirable for clinical applications [27]. However, it should be noted that values of Cronbach’s a approaching one (1), or perfect association of items, indicate redundancy in the scale [26]. In addition, an ‘item-rest’ analysis examined the influence of individual items on the internal consistency of the scale. The analysis re-calculates alpha after removing (resting) the responses to a particular question. The analysis is interpreted such that a lower item-rest correlation indicates that the item contributes to the internal consistency, for the particular domain of the scale.
2.4.2.
2.6.
Ethics
This study was approved by the RPH Ethics Committee (#2012/ 109). The approval further granted an extension of the waiver of consent provision previously approved for collection of outcome questionnaire data (#2009/065).
Validity
To confirm criterion validity, the BFI must demonstrate a significant negative correlation with BSHS-B total with increasing time after injury. To assess criterion validity, a multivariate analysis was used to model the relationship of BFI with BSHS-B total score over time. A forward selection method was used to identify variables to be included in the models, based on their univariate p-values ( p < 0.10). Each assessment timepoint comparison used the one month after burn outcomes as the reference category. As the BSHS-B data were skewed and could not be readily transformed, a quantile regression was used as it regresses the outcome variable towards the median. This was a more suitable representation of the dataset and minimised the bias of heteroskedasticity which was evident in the BSHS-B data. A ‘per-patient’ cluster adjustment was performed due to the repeated measures of the BSHS-B and BFI scores and variation in number of assessments contributed by each patient into the dataset. For the multivariable regression analyses, significance was set as p < 0.05. The construct validity of the BFI was assessed initially using a factor analysis which also defined the number of domains in the scale. Domains or factors were identified based on the eigenvalues. The eigenvalue indicated the proportion of variance accounted for by each factor which contained one or more questions of a similar construct. The greater the eigenvalue, the larger the proportion of variance accounted for. As per Guttman (1954), eigenvalues greater than one were considered significant [28]. A second analysis was used to assess longitudinal construct validity using the BFI quantitation of fatigue for minor and major burns over time. The pattern was described and compared using a random effects longitudinal model including all significant interaction terms. After testing for interactions and including significant covariates again using a forward selection method, a final multivariate model was constructed to determine the overall difference in fatigue scores between minor and major burns. Although the BFI’s distribution was skewed, its means and medians were similar at each time-point and amenable to bootstrapping, which allowed p-values to be determined independent of normality assumptions.
2.5.
bias due to loss to follow-up of patients with less severe burn was addressed through: (a) choice of robust multivariable regression analyses and (b) imputation of data to provide more robust error estimates of longitudinal outcomes (bootstrapping 500).
Missing data
Missing data in the first year after burn were expected in the predominantly minor burn cohort at RPH. Thus, to minimise
3.
Results
3.1.
Sample characteristics
A total of 587 patients treated for their burns at RPH were recruited during the study period, resulting in 1059 paired questionnaires (BFI and BSHS-B) available for analysis. For the WA patients in this study, the summed fatigue scores ranged from 0 to 90 with a median of 13 (Q1–Q3 = 3–32). Males represented 68.8% of the cohort; age ranged from 14 to 87 years with a median of 36 (Q1–Q3: 24–52) and TBSA ranged from 0.73 indicating a good level of internal consistency, despite individual item response removal. These results imply excellent internal consistency of the BFI when used to assess fatigue in patients with burns at all time-points in the study.
3.3.
Criterion validity
Criterion validity was confirmed at one month by the negative association of BSHS-B total and BFI ( p < 0.001) (Table 2). However, for those with a BFI of zero i.e. without fatigue, compared to one month, no significant associations were detected at the other assessment times ( p = 0.53, 0.45 and 0.09 for three, six and 12 months, respectively). These results were confirmed by repeating the quantile regression analyses, using each respective assessment timepoint as reference. Fatigue as measured by BFI global score was not associated significantly with change in BSHS-B at the later timepoints (analyses not presented). The significant interaction terms and coefficients confirm that the magnitude of
Table 1 – Sample demographics of patients who returned for follow-up at each time-point. All
Minor burns
Major burns
One
Three
Six
Twelve
One
Three
Six
Twelve
One
Three
Six
Twelve
Number of patients Length of stay Median (Q1–Q3)a
393 7 (3–12)
287 7 (2–12)
217 7.5 (2–12)
153 8 (4–12)
337 6 (3–10)
246 6 (2–10)
190 6 (2–11)
132 7 (4–11)
43 19 (15–30)
33 21 (16–41)
25 16 (11–53)
21 20 (12–57)
Age
Median (Q1–Q3)
34 (24–51)
37 (24–53)
39 (26–55)
39 (25–56)
34 (24–52)
38 (24–54)
40 (26–56)
40 (26–56)
28 (23–51)
28 (24–53)
27 (24–56)
26 (23–56)
TBSA
Median (Q1–Q3)
3 (1–7)
3 (1–8)
3 (1–8)
3 (1–10)
3 (1–5)
2 (1–5)
2.85 (1–5)
2.5 (1–6)
21 (15–27)
21 (16–29)
18 (15–33)
20 (15–25)
Global BFI
Median (Q1–Q3)
2 (1–5)
2 (1–4)
2 (1–4)
1 (1–4)
2 (1–5)
2 (1–3)
1.5 (1–3)
1 (0–3)
4 (2–6)
3 (1–6)
5 (1–7)
2 (1–5)
BSHS-B
Median (Q1–Q3)
140 (120–153)
147.5 (132–157)
149 (129–158)
152 (135–159)
142 (123–155)
150 (136–158)
151 (136–158)
153 (139–159)
124 (100–141)
128 (106–143)
119 (94–146)
144 (116–154)
% Males % Surgery
68.7 78
67.9 77.5
68.7 75.6
64.5 81
68.5 76.9
66.2 74.0
67.4 73.2
62.9 78.0
72.1 86.0
78.8 93.9
80.0 84.0
71.4 90.5
burns 41 (2015) 990–997
Months from burn
a
Q1 = Quartile 1 or 25th percentile and Q3 = Quartile 3 or 75th percentile. NB: The 20 patients without a recorded TBSA are not included under minor and major (>15% TBSA) burns. At one month, 13 patients had no recorded TBSA; at three months, eight patients had no recorded TBSA; and at six months, two patients had no recorded TBSA.
993
994
burns 41 (2015) 990–997
Table 2 – Multivariable quantile regression predicting BSHS-B total score over time. Coefficient BFI Three months Six months 12 months Three months T BFIa Six months T BFIa 12 months T BFIa TBSA Females Constant a
6.42 0.70 0.93 2.05 1.35 1.53 1.90 0.54 3.00 160.11
p
95% CI
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/locate/burns
The Brief Fatigue Inventory is reliable and valid for the burn patient cohort Christopher Toh a,b, Marie Li a,b, Vidya Finlay c, Teresa Jackson c, Sally Burrows b,d, Fiona M. Wood a,c,e, Dale W. Edgar a,c,f,* a
Burn Service of WA, Royal Perth Hospital, WA, Australia School of Medicine and Pharmacology, University of Western Australia, Australia c Fiona Wood Foundation, Perth, WA, Australia d Perkins Medical Research Institute, Perth, WA, Australia e Burn Injury Research Unit, University of Western Australia, Australia f Burn Injury Research Node, Institute of Health and Rehabilitation Research, University of Notre Dame, Fremantle, WA, Australia b
article info
abstract
Article history:
Objective: After burn, patients are at risk of fatigue which may influence negatively their
Received 18 September 2014
capacity to participate in activity, rehabilitation and other treatments. Fatigue may stem
Received in revised form
from the wound healing and systemic responses to burn which drive a hypermetabolic state
16 November 2014
that may persist for months. However, an established method is not available for objectively
Accepted 19 November 2014
measuring fatigue after burns. The Brief Fatigue Inventory (BFI) was hypothesised to be an appropriate option for assessments following severe burn. The primary aim of the study was to establish if the BFI was reliable and valid in a burn patient sample.
Keywords:
Methods: Adult patients admitted between 2009 and 2013 to Royal Perth Hospital Burn
Acute burns
Center were included. Patients completed the BFI and Burns Specific Health Scale Brief
Fatigue
(BSHS-B) in tandem at one, three, six and 12 months after burn. Reliability was assessed
Quality of life
using Cronbach’s alpha; construct validity using factor analysis and multi-variable regres-
Participant response outcome
sion of BFI; and, criterion validity with longitudinal regression of BFI with BSHS-B. Results: The sample (n = 587) had a median TBSA of 3% (range = 0.90). The factor analysis confirmed a single-domain construct, centred around the first scale item. Good correlation between BFI and BSHS-B scores ( p < 0.001) on longitudinal analysis confirmed criterion validity. There was a significant difference in fatigue scores between minor and major burn patients and a significant association of fatigue levels over time with TBSA. Conclusion: The BFI is a reliable and valid tool for fatigue measurement in patients during the first 12 months after burn. # 2014 Elsevier Ltd and ISBI. All rights reserved.
* Corresponding author at: Burn Service of WA, Royal Perth Hospital, WA, Australia. Tel.: +61 8 9224 3566; fax: +61 8 9224 3577. E-mail address: [email protected] (D.W. Edgar). http://dx.doi.org/10.1016/j.burns.2014.11.014 0305-4179/# 2014 Elsevier Ltd and ISBI. All rights reserved.
burns 41 (2015) 990–997
1.
Introduction
Fatigue is a distressing symptom reported by patients suffering from a wide range of medical conditions [1,2]. It is a symptom that patients with burns commonly experience [3], possibly due to the hypermetabolic response that occurs after injury [4]. The response is exacerbated by impairments in muscle and physical function, which further contribute to higher fatigue levels [4]. In larger injuries, increased cardiac work, raised body temperature and futile substrate cycling also make fatigue a more likely symptom [4,5]. In addition, the hypermetabolic changes persist long after the initial burn [4,5]. Despite the obvious precursors to fatigue in burn patients and evidence that fatigue significantly influences vitality and quality of life (QoL), it is rarely assessed by clinicians [1,2,6]. That said, to date, an instrument for measuring fatigue has not been proposed or assessed for its use after burn. The Brief Fatigue Inventory (BFI) is one such self-report tool developed originally to measure fatigue levels in cancer patients [7]. Its utility is confirmed in other conditions such as stroke and rheumatoid arthritis [8,9]. It is shorter and easier to understand than other fatigue assessment tools available [7]. The primary aim of this study was to determine if the BFI is a reliable and valid longitudinal measure of fatigue levels in a burn patient cohort. In addition, as part of the validity assessment, the study was designed to quantify the BFI performance in measuring differences between minor and major burns, in order to inform clinical recommendations for the BFI’s use by clinicians and researchers.
2.
Methods
The specific hypotheses included: (a) the internal reliability (Cronbach’s alpha) of BFI is 0.9, (b) The BFI has a significant relationship with the Burn Specific Health Scale-Brief over time (criterion validity), (c) the construct validity of the scale items is confirmable by factor analysis and (d) the BFI shows a difference in fatigue levels between minor and major (>15% TBSA) burns (sensitivity and construct validity).
2.1.
Study design and data collection
This study was a statistical assessment of the performance of the BFI in a single-centre cohort of adult burn patients. This was achieved through analysis of retrospective data, prospectively collected from patients treated for burns treated at Royal Perth Hospital (RPH), between November 2009 and July 2013. Patients were included, irrespective of possible effect modifiers, such as age, gender and mode or severity of injury. Patients were excluded if they were unable to complete the questionnaires due to intellectual capacity or if an appropriate interpreter was unavailable, as all surveys were provided in written English. The cohort included both inpatients and ambulatory patients, thus examined a broad spectrum of injury severity. The BFI and the Burn Specific Health Scale Brief (BSHS-B) questionnaires were collected in tandem in person if and when the patient attended the hospital, or by mail, at one, three, six and 12 months after burn.
2.2.
991
Brief Fatigue Inventory (BFI)
The BFI has nine (9) questions scored on a 0–10 point numeric scale such that the maximum possible fatigue (summation) score is 90 (Appendix I). The survey is presented as two parts, with the first three questions rating current, usual and worst levels of fatigue over the past 24 h. The remaining six questions request a rating of the impact of fatigue on: activity, mood, walking, work, relationships and enjoyment of life. A global BFI score may be calculated by taking the mean of the nine questions, with a higher score indicating a greater level of fatigue. In that, the maximum possible global fatigue level reportable on the scale is 10. The BFI was chosen over other instruments to minimise patient burden and as the questions are in simple language. Instruments such as the Functional Assessment of Cancer Therapy–Fatigue (FACT–F) (47 items) and the Multidimensional Fatigue Inventory (58 items) are much longer than the BFI [10,11]. The Pearson–Byars Fatigue Feeling Checklist uses more colloquial expressions like ‘‘fairly well pooped’’ and ‘‘very lively’’ [12] which are more difficult to translate for nonEnglish speaking respondents. The simple expressions used in the BFI may also be the reason that it is popularly chosen for validation in a number of other languages [13–20]. In addition, despite being concise, the BFI still correlates well with other well-established instruments such as the FACT–F and the Profile of Mood States Fatigue subscale [10,21].
2.3.
Burns specific health scale-brief
The BSHS-B is a 40-item disease specific questionnaire widely used to assess QoL outcomes after a burn [22]. This version was modified from the original BSHS, which consisted of 114 questions [23] but was shown to be equally sensitive [24]. BSHS-B has excellent internal consistency indicating the high level of reliability of the tool, which was confirmed for major and recently, minor burns [24,25]. With time after burn the BSHS-B score is expected to increase indicating recovery and improvement of quality of life.
2.4.
Statistical methods
Statistical analyses were conducted using STATA (v.12 Statacorp, Texas). Descriptive statistics of patient demographics were presented as median, upper and lower quartiles of the inter-quartile range (Q1–Q3) where the variables are continuous, or as percentages where they are categorical. Variables which were identified as possible factors that influence fatigue levels in burns, trauma and other patient populations were examined as covariates in all multivariable models. These included: time since injury, age, gender, injury severity markers and their interaction terms. The severity markers included total burn surface area [TBSA] and category of burn (where major burn was defined as >15% TBSA).
2.4.1.
Reliability
The BFI survey was assessed for internal consistency, as a measure of reliability, using Cronbach’s alpha calculated from all available responses. The greater the value of alpha, the
992
burns 41 (2015) 990–997
greater its internal consistency [26]. Bland and Altman (1997) recommended an alpha 0.9 is desirable for clinical applications [27]. However, it should be noted that values of Cronbach’s a approaching one (1), or perfect association of items, indicate redundancy in the scale [26]. In addition, an ‘item-rest’ analysis examined the influence of individual items on the internal consistency of the scale. The analysis re-calculates alpha after removing (resting) the responses to a particular question. The analysis is interpreted such that a lower item-rest correlation indicates that the item contributes to the internal consistency, for the particular domain of the scale.
2.4.2.
2.6.
Ethics
This study was approved by the RPH Ethics Committee (#2012/ 109). The approval further granted an extension of the waiver of consent provision previously approved for collection of outcome questionnaire data (#2009/065).
Validity
To confirm criterion validity, the BFI must demonstrate a significant negative correlation with BSHS-B total with increasing time after injury. To assess criterion validity, a multivariate analysis was used to model the relationship of BFI with BSHS-B total score over time. A forward selection method was used to identify variables to be included in the models, based on their univariate p-values ( p < 0.10). Each assessment timepoint comparison used the one month after burn outcomes as the reference category. As the BSHS-B data were skewed and could not be readily transformed, a quantile regression was used as it regresses the outcome variable towards the median. This was a more suitable representation of the dataset and minimised the bias of heteroskedasticity which was evident in the BSHS-B data. A ‘per-patient’ cluster adjustment was performed due to the repeated measures of the BSHS-B and BFI scores and variation in number of assessments contributed by each patient into the dataset. For the multivariable regression analyses, significance was set as p < 0.05. The construct validity of the BFI was assessed initially using a factor analysis which also defined the number of domains in the scale. Domains or factors were identified based on the eigenvalues. The eigenvalue indicated the proportion of variance accounted for by each factor which contained one or more questions of a similar construct. The greater the eigenvalue, the larger the proportion of variance accounted for. As per Guttman (1954), eigenvalues greater than one were considered significant [28]. A second analysis was used to assess longitudinal construct validity using the BFI quantitation of fatigue for minor and major burns over time. The pattern was described and compared using a random effects longitudinal model including all significant interaction terms. After testing for interactions and including significant covariates again using a forward selection method, a final multivariate model was constructed to determine the overall difference in fatigue scores between minor and major burns. Although the BFI’s distribution was skewed, its means and medians were similar at each time-point and amenable to bootstrapping, which allowed p-values to be determined independent of normality assumptions.
2.5.
bias due to loss to follow-up of patients with less severe burn was addressed through: (a) choice of robust multivariable regression analyses and (b) imputation of data to provide more robust error estimates of longitudinal outcomes (bootstrapping 500).
Missing data
Missing data in the first year after burn were expected in the predominantly minor burn cohort at RPH. Thus, to minimise
3.
Results
3.1.
Sample characteristics
A total of 587 patients treated for their burns at RPH were recruited during the study period, resulting in 1059 paired questionnaires (BFI and BSHS-B) available for analysis. For the WA patients in this study, the summed fatigue scores ranged from 0 to 90 with a median of 13 (Q1–Q3 = 3–32). Males represented 68.8% of the cohort; age ranged from 14 to 87 years with a median of 36 (Q1–Q3: 24–52) and TBSA ranged from 0.73 indicating a good level of internal consistency, despite individual item response removal. These results imply excellent internal consistency of the BFI when used to assess fatigue in patients with burns at all time-points in the study.
3.3.
Criterion validity
Criterion validity was confirmed at one month by the negative association of BSHS-B total and BFI ( p < 0.001) (Table 2). However, for those with a BFI of zero i.e. without fatigue, compared to one month, no significant associations were detected at the other assessment times ( p = 0.53, 0.45 and 0.09 for three, six and 12 months, respectively). These results were confirmed by repeating the quantile regression analyses, using each respective assessment timepoint as reference. Fatigue as measured by BFI global score was not associated significantly with change in BSHS-B at the later timepoints (analyses not presented). The significant interaction terms and coefficients confirm that the magnitude of
Table 1 – Sample demographics of patients who returned for follow-up at each time-point. All
Minor burns
Major burns
One
Three
Six
Twelve
One
Three
Six
Twelve
One
Three
Six
Twelve
Number of patients Length of stay Median (Q1–Q3)a
393 7 (3–12)
287 7 (2–12)
217 7.5 (2–12)
153 8 (4–12)
337 6 (3–10)
246 6 (2–10)
190 6 (2–11)
132 7 (4–11)
43 19 (15–30)
33 21 (16–41)
25 16 (11–53)
21 20 (12–57)
Age
Median (Q1–Q3)
34 (24–51)
37 (24–53)
39 (26–55)
39 (25–56)
34 (24–52)
38 (24–54)
40 (26–56)
40 (26–56)
28 (23–51)
28 (24–53)
27 (24–56)
26 (23–56)
TBSA
Median (Q1–Q3)
3 (1–7)
3 (1–8)
3 (1–8)
3 (1–10)
3 (1–5)
2 (1–5)
2.85 (1–5)
2.5 (1–6)
21 (15–27)
21 (16–29)
18 (15–33)
20 (15–25)
Global BFI
Median (Q1–Q3)
2 (1–5)
2 (1–4)
2 (1–4)
1 (1–4)
2 (1–5)
2 (1–3)
1.5 (1–3)
1 (0–3)
4 (2–6)
3 (1–6)
5 (1–7)
2 (1–5)
BSHS-B
Median (Q1–Q3)
140 (120–153)
147.5 (132–157)
149 (129–158)
152 (135–159)
142 (123–155)
150 (136–158)
151 (136–158)
153 (139–159)
124 (100–141)
128 (106–143)
119 (94–146)
144 (116–154)
% Males % Surgery
68.7 78
67.9 77.5
68.7 75.6
64.5 81
68.5 76.9
66.2 74.0
67.4 73.2
62.9 78.0
72.1 86.0
78.8 93.9
80.0 84.0
71.4 90.5
burns 41 (2015) 990–997
Months from burn
a
Q1 = Quartile 1 or 25th percentile and Q3 = Quartile 3 or 75th percentile. NB: The 20 patients without a recorded TBSA are not included under minor and major (>15% TBSA) burns. At one month, 13 patients had no recorded TBSA; at three months, eight patients had no recorded TBSA; and at six months, two patients had no recorded TBSA.
993
994
burns 41 (2015) 990–997
Table 2 – Multivariable quantile regression predicting BSHS-B total score over time. Coefficient BFI Three months Six months 12 months Three months T BFIa Six months T BFIa 12 months T BFIa TBSA Females Constant a
6.42 0.70 0.93 2.05 1.35 1.53 1.90 0.54 3.00 160.11
p
95% CI
