Archives of Physical Medicine and Rehabilitation journal homepage: www.archives-pmr.org Archives of Physical Medicine and Rehabilitation 2014;-:-------
Comparison of the Test-Retest Reliability of the Balance Computerized Adaptive Test and a Computerized Posturography Instrument in Patients With Stroke Chia-Hsin Chen, MD, PhD,a,b,c,* Shih-Feng Lin, BS,a,* Wan-Hui Yu, MS,d Jau-Hong Lin, PhD,e,f Hao-Ling Chen, PhD,d Ching-Lin Hsieh, PhDd From the aDepartment of Physical Medicine and Rehabilitation, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung; bDepartment of Physical Medicine and Rehabilitation, Kaohsiung Medical University Hospital, Kaohsiung; cDepartment of Physical Medicine and Rehabilitation, School of Medicine, Graduate Institute of Neuroscience, College of Medicine, Kaohsiung Medical University, Kaohsiung; dSchool of Occupational Therapy, College of Medicine, National Taiwan University, Taipei City; eDepartment of Physical Therapy, College of Health Science, Kaohsiung Medical University, Kaohsiung; and fDepartment and Graduate Institute of Neurology, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan. *Chen and Lin contributed equally to this work.
Abstract Objective: To compare the test-retest reliabilities of the scores of the Balance Computerized Adaptive Test (CAT) and the Biodex Balance System in patients with stroke. Design: A repeated-measures design (at a 1-wk interval) was used to examine the test-retest reliabilities of the scores of the Balance CAT and the Biodex Balance System. Setting: One rehabilitation unit in a local hospital. Participants: Patients (NZ50) with stroke for more than 6 months and undergoing outpatient rehabilitation completed the Balance CAT and the eyes open (EO)/closed (EC) tests, but only 17 patients finished the Limit of Stability (LOS) test because they were unable to reach all the targets. Interventions: Not applicable. Main Outcome Measures: The Balance CAT and 2 computerized tests of the Biodex Balance System, namely the EO/EC test and the LOS, were used to evaluate balance function. Results: The test-retest reliabilities of the scores of the Balance CAT (Pearson rZ.92, minimal detectable change [MDC] percentZ12.8%) was excellent. Those of the EO/EC and LOS tests were poor to good (Pearson rZ.56e.85, MDC%Z50.8%e126.9%). Conclusions: The test-retest reliabilities of the scores of the Balance CAT were sufficient for assessing balance function in patients with stroke. Moreover, the test-retest reliabilities of the scores of the Balance CAT, one of the functional balance measures, were superior to those of the Biodex Balance System, 1 type of computerized posturography instrument. Therefore, the Balance CAT may be a more reliable measure for clinicians and researchers to use in assessing the balance function of patients with stroke for more than 6 months. Archives of Physical Medicine and Rehabilitation 2014;-:------ª 2014 by the American Congress of Rehabilitation Medicine
A deficit in balance is a common problem in patients with stroke. This deficit may seriously impair their function in activities of Supported by Kaohsiung Municipal Ta-Tung Hospital in Taiwan (grant no. KMTTH-100-026). Disclosures: none.
daily living such as walking and stair climbing, thereby increasing the risk of falling.1-4 Improving balance function is an important goal of rehabilitation.5 Through the use of reliable functional balance measurements, clinicians can effectively assess and monitor the balance function of patients with stroke.6,7
0003-9993/14/$36 - see front matter ª 2014 by the American Congress of Rehabilitation Medicine http://dx.doi.org/10.1016/j.apmr.2014.03.005
C-H Chen et al
Functional balance measures, which assess balance function through functional tasks, are one type of balance measure frequently used in clinical and research settings. These functional balance measures, such as the Berg Balance Scale and Postural Assessment Scale for Stroke Patients (PASS), have practical advantages, including ease of use and low cost.8 Unfortunately, few of them can achieve both efficiency and precision, both of which are needed in busy clinics. Computerized adaptive testing has been suggested to meet this need.9,10 The Balance Computerized Adaptive Test (CAT) has been developed to efficiently and precisely assess balance function in patients with stroke through a computerized adaptive testing system.11 The Balance CAT chooses items tailored to an individual patient and skips items that are too easy or too difficult for that patient. This advantage allows clinicians to efficiently assess balance function when time is limited. Some psychometric properties of the scores of the Balance CAT in inpatients with stroke receiving rehabilitation, namely the responsiveness and predictive validity, have been verified.12 However, the test-retest reliability of the Balance CAT in patients with stroke has not been examined. Apart from functional balance scales, another type of balance measure is computerized posturography instruments, such as the Smart Balance Master System (SBM) and Biodex Balance System.a This type of balance measure has been developed to objectively quantify standing balance function with high resolution and thus help clinicians precisely monitor the changes in patients’ balance function.13,14 Objective quantification with high resolution is thought to be helpful for yielding better test-retest reliability (eg, test-retest reliability). Thus, the test-retest reliabilities of the scores of computerized posturography instruments in patients with stroke might be better than those of functional balance scales. Recently, the Biodex Balance System, which is less expensive and more portable than the SBM, has frequently been used in clinical or sports rehabilitation settings.15 However, since no studies have examined the test-retest reliabilities of the scores of the Biodex Balance System in patients with stroke, its utility in such patients is limited. Although the Biodex Balance System and the Balance CAT measure balance function in different ways, both are frequently used to represent and monitor the balance function of patients in clinics and research. Before these balance measures are used, their test-retest reliabilities must be confirmed, compared head to head, or both. Therefore, the purposes of the study were to compare the test-retest reliabilities and random measurement errors (ie, minimal detectable change [MDC]) of the Biodex Balance System and Balance CAT in patients with chronic stroke. The results should be useful for both clinicians and researchers in selecting an appropriate balance measure for patients with chronic stroke. We hypothesized that the test-retest reliabilities of the scores of the Biodex Balance System, which can objectively quantify balance function with high resolution, would be superior to that of a functional balance measure, namely the Balance CAT.
List of abbreviations: CAT EC EO LOS MDC PASS SBM SEM
Computerized Adaptive Test eyes closed eyes open limit of stability minimal detectable change Postural Assessment Scale for Stroke Patients Smart Balance Master System standard error of measurement
Methods Participants We recruited patients undergoing outpatient rehabilitation in an urban rehabilitation center, which provides typical stroke rehabilitation. The following criteria were used to determine whether patients could be included in this study: (1) diagnosis of cerebral hemorrhage or cerebral infarction; (2) stroke onset >6 months before the start of the study (ie, chronic patients); (3) ability to stand without assistive devices for 30 seconds; (4) ability to follow instructions to complete the assessments; (5) no visual impairment; and (6) absence of other neuromusculoskeletal diseases (eg, Parkinsonism, osteoarthritis) that could affect a patient’s balance function. Patients who met the inclusion criteria were invited by a trained physical therapist (S.-F.L.) to join our study. All the invited patients participated in our study. Informed consent for participation was obtained from the participants personally or by proxy. Patients who had previously been trained in using the Biodex Balance System were excluded in this study. This study was approved by the institutional review boards of local ethics committees.
Procedures Demographic data were collected from all participants before testing to determine the general characteristics of the sample population. All subjects were evaluated initially using the Balance CAT and the Biodex Balance System and were then reassessed after 1-week intervals. For each subject, both measures in the testretest sessions were administered by the physical therapist (S.-F.L.) in a counterbalanced order within 24 hours. To ensure that the subjects’ conditions were stable during the study period, changes in their medical conditions between the 2 assessments were recorded. We excluded 13 subjects who developed recurrent strokes or other medical conditions that might result in poorer performance in balance during the test-retest period.
Measures Balance CAT The Balance CAT is a computerized adaptive test developed to evaluate balance function in patients with stroke.11 This measure contains a pool of 34 easily administered items that can be administered by a clinician using a personal digital device connected to the Internet. The resulting scores, transformed using item response theory, range from 0 to 10. The Balance CAT chooses items tailored to an individual patient’s balance function and skips items that are too easy or too difficult for the patient. For example, if a patient cannot stand independently, the system will not select a more difficult task (eg, stand on 1 leg) for further testing. Instead, the system will select an easier task (eg, sit without support). In general, the Balance CAT takes only 4 items (completed within 2min on average) to obtain reliable and valid balance assessments of patients with stroke.11,12 For all the testing with the Balance CAT, the subjects wore their own shoes. The feasibility of the Balance CAT in patients with stroke, in terms of sufficient validity and responsiveness, has been previously determined in inpatients with stroke.11,12 Biodex Balance System The Biodex Balance System, a commercially available device, is used to quantify and train the ability of standing balance in www.archives-pmr.org
Reliability of Balance Computerized Adaptive Test and Biodex
patients with pathologic conditions.16 In this study, the subjects were instructed to stand independently on the platform without footwear, keeping their feet apart at a distance equal to the width of the shoulders and their arms by their sides, without support. In the Biodex Balance System, the Clinical Test of Sensory Integration and the Balance and Limit of Stability (LOS) tests were used. Since patients with stroke may have poor balance function, only the eyes open/eyes closed (EO/EC) tests on a firm surface were used in the present study because of safety considerations. For each trial of each condition, subjects were encouraged to maintain a stable upright posture for 30 seconds. Two trials were performed for each test condition, with resting periods of 10 seconds between trials and 5 minutes between conditions. The measures of the EO/EC test were the stability index (EOstability/EC-stability) and the sway index (EO-sway/EC-sway). High scores in the stability index and the sway index indicate poor balance.16 For the LOS test, subjects were instructed to shift their center of gravity to move a ball-shaped cursor from the center target to a blinking target and back as quickly and with as little deviation as possible, keeping their body in a straight line, with the ankle joint as the primary axis of rotation. Three trials were performed, with resting periods of 3 minutes between trials. The target placement was preset by the Biodex Balance System at 50% of the theoretical LOS, based on the subject’s height. Before testing, 1 practice trial was performed. The measures of the LOS test were the duration to reach all targets (LOS-time) and the overall directional control score (LOS-overall control). Higher scores in overall directional control and lower scores in duration indicate better dynamic postural control.16 For each condition, the average of trial data was used for subsequent analysis.
Data analysis Data were analyzed with the IBM SPSS Statistics 19.0 program.b To investigate the test-retest reliability of the Balance CAT and the Biodex Balance System, the Pearson correlation coefficient was used. A Pearson r value >.75 indicates good reliability (>.90, excellent); .50 to .75, moderate to good reliability; and