Test-retest reliability and responsiveness of the Barthel Index-based Supplementary Scales in patients with stroke.

Background: A lack of evidence on the test-retest reliability and responsiveness limits the utility of the BI-based Supplementary Scales (BI-SS) in both clinical and research settings.

Aim: To examine the test-retest reliability and responsiveness of the BI-based Supplementary Scales (BI-SS) in patients with stroke.

Design: A repeated-assessments design (1 week apart) was used to examine the test-retest reliability of the BI-SS. For the responsiveness study, the participants were assessed with the BI-SS and BI (treated as an external criterion) at admission to and discharge from rehabilitation wards.

Setting: Seven outpatient rehabilitation units and one inpatient rehabilitation unit.

Population: Outpatients with chronic stroke.

Methods: Eighty-four outpatients with chronic stroke participated in the test-retest reliability study. Fifty-seven inpatients completed baseline and follow-up assessments in the responsiveness study.

Results: For the test-retest reliability study, the values of the intra-class correlation coefficient and the overall percentage of minimal detectable change for the Ability Scale and Self-perceived Difficulty Scale were 0.97, 12.8%, and 0.78, 35.8%, respectively. For the responsiveness study, the standardized effect size and standardized response mean (representing internal responsiveness) of the Ability Scale and Self-perceived Difficulty Scale were 1.17 and 1.56, and 0.78 and 0.89, respectively. Regarding external responsiveness, the change in score of the Ability Scale had significant and moderate association with that of the BI (r=0.61, P<0.001). The change in score of the Self-perceived Difficulty Scale had non-significant and weak association with that of the BI (r=0.23, P=0.080).

Conclusions: The Ability Scale of the BI-SS has satisfactory test-retest reliability and sufficient responsiveness for patients with stroke. However, the Self-perceived Difficulty Scale of the BI-SS has substantial random measurement error and insufficient external responsiveness, which may affect its utility in clinical settings.

Clinical Rehabilitation Impact: The findings of this study provide empirical evidence of psychometric properties of the BI-SS for assessing ability and self-perceived difficulty of ADL in patients with stroke.