Estimating the minimal clinically important difference for the Physical Component Summary of the Short Form 36 for patients with stroke

Objective To determine the Physical Component Summary (PCS) score's minimal clinically important difference (MCID) on the Short Form 36 (SF-36) for people with stroke. Methods We conducted secondary analysis of data from a large randomized controlled trial (N = 400) in the post-hospital discharge phase of stroke rehabilitation with outcome measurement 6 and 12 months following stroke. Three methods were used for estimating the MCID: two anchor and one distribution. Method 1 compared SF-36 PCS scores at 12 months for responses to the SF-36's Perceived Health Change (PHC) question. Method 2 compared the change in PCS score between 6 and 12 months for responses to the PHC question. Method 3 used Cohen's method to estimate the MCID from the PCS score distribution. Results Method 1: the mean PCS score increased by 3.0 units (95% confidence interval [CI] 2.2-3.9) for each unit change in the PHC question. Method 2: the mean change in PCS score increased by 2.1 units (95% CI 1.4-2.8) for each unit change in the PHC question. Method 3: the MCID was estimated to be 1.8 units. Conclusions Our estimate of the MCID for the PCS in patients with stroke was 1.8 to 3.0 units.