Responsiveness and predictive validity of the sitting balance scale and function in sitting test in people with stroke
A common impairment following stroke is impaired balance. Many survivors of stroke are non-ambulatory. Using a valid, reliable, and sensitive measurement tool is essential to identifying balance impairment accurately and making informed clinical decisions. Limited studies examined qualities of available sitting balance scales. The purpose of this study was to examine the responsiveness and the predictive validity of the Sitting Balance Scale (SBS) and Function in Sitting Test (FIST), in people in sub-acute rehabilitation settings who have had a stroke. We also aimed to establish the minimal detectable change (MDC) and minimal clinically important differences (MCID) for both scales. We recruited 40 participants with stroke who were tested upon admission and shortly before discharge. The effect size (ES) and the standardized response mean (SRM) were used as indicators of internal responsiveness. Using Pearson’s correlation coefficient, the external responsiveness was tested by examining the association between the difference in scores on the SBS or FIST and the difference in scores on the Barthel Index (BI). Univariate linear regression and the receiver operating characteristic (ROC) curve were used to examine predictive validity. The MDC, 90% confident level (MDC90) was calculated from the standard error of measurement, while anchor-based and distribution-based approaches were used to establish the values of MCID. Both scales demonstrated sufficient internal (ES & SRM > 1.11) and external responsiveness (r > 0.6). The SBS demonstrated better internal responsive than the FIST. Both scales were equally useful in predicting discharge placement (area under the curve > 0.81). However, the SBS demonstrated better predictive power in predicting functional level than the FIST (SBS, R2 = 0.53; FIST, R 2 = 0.43). Both scales failed to predict length of stay. The MDC 90 values were estimated for the SBS and the FIST to be, 2.32 and 3.9 respectively. Therefore, when a change in score between two measurement occasions exceeds 2.32 on the SBS or 3.9 on the FIST, clinicians can be 90% confident in interpreting the change as error free. We established the MCID for both scales as follows: the SBS, 5 points; the FIST, 6 points. The established MDCs and MCIDs may help clinicians to interpret the change in performance and verify treatment effects after stroke rehabilitation. The results of this study support the usefulness of two well-designed sitting balance tools in people following a stroke. Using these tools will help clinicians effectively address sitting balance during early rehabilitation phases. As supported by this study, restoring sitting balance will help to improve a patient’s functional level at discharge. Patients with sufficient functional level are likely to be discharged home, rather than to long-term care.