Responsiveness and minimal clinically important difference of Modified Ashworth Scale in patients with stroke

BACKGROUND: Spasticity is a major problem in patients with stroke and influences their activities of daily living, participation, and quality of life. The Modified Ashworth Scale is widely used to assess spasticity. However, the responsiveness and minimal clinically important differences of the Modified Ashworth Scale in patients with stroke have not been explored. AIM: This study aims to examine the responsiveness and minimal clinically important differences of the Modified Ashworth Scale in patients with stroke. DESIGN: Longitudinal six-month follow-up study. SETTING: Rehabilitation wards of a tertiary hospital. POPULATION: One-hundred and fifteen patients with stroke were recruited. METHODS: All patients underwent the assessment of Modified Ashworth Scale for the upper extremity (flexors of the elbow, wrist, and fingers) and the lower extremity (hip adductor, knee flexor, and ankle plantar flexor) at baseline and 6-month follow-up. The average Modified Ashworth Scale scores of the upper and lower extremity muscles were obtained for analysis. Responsiveness of the Modified Ashworth Scale was determined using standardized mean response, and the minimal clinically important differences were determined using a distribution-based approach with Effect Sizes of 0.5 and 0.8 standard deviations. RESULTS: The responsiveness of the Modified Ashworth Scale in the upper and lower extremity muscles was marked (standardized response mean = 0.89-1.09). The minimal clinically important differences of the average Modified Ashworth Scale of Effect Sizes 0.5 and 0.8 standard deviations for the upper extremity muscles were 0.48 and 0.76, respectively, while those for the lower extremity muscles were 0.45 and 0.73, respectively. CONCLUSIONS: The Modified Ashworth Scale was markedly responsive in detecting the changes in muscle tone in patients with stroke. The minimal clinically important differences of the Modified Ashworth Scale reported in this study can be used by researchers and clinicians in determining whether the observed changes are clinically meaningful post-treatment or at follow-up. CLINICAL REHABILITATION IMPACT: The minimal clinically important differences of the Modified Ashworth Scale reported in this study will enable clinicians and researchers in determining whether changes in the muscle tone are true and clinically meaningful, and can be used as a reference for clinical decision-making. Key words: stroke, muscle spasticity, minimal clinically important difference, psychometrics