A comparison of 3 methodological approaches to defining major clinically important improvement of 4 performance measures in patients with hip osteoarthritis

Prospective cohort study. To establish the major clinically important improvement (MCII) of the timed up-and-go test (TUG), 40-meter self-paced walk test (40-m SPWT), 30-second chair stand (30 CST), and a 20-cm step test in patients with hip osteoarthritis (OA) undergoing physiotherapy treatment. As a secondary aim, a comparison of methods was employed to evaluate the effect of method on the reported MCII. Minimal clinically important difference scores are commonly used by rehabilitation professionals to determine patient response following treatment. A gold standard for calculating MCII has yet to be determined, which has resulted in problems of interpretation due to varied results. As part of a randomized controlled trial, 65 patients were randomized into a physiotherapy treatment group for hip OA, in which they completed 4 physical performance measures at baseline and 9 weeks. Upon completion of physiotherapy, patients assessed their response to treatment on a 15-point global rating of change scale (GRCS). MCII was estimated using 3 variations of an anchor-based method, based on the patient's opinion. A comparison of 3 methods resulted in the following change scores being best associated with our definition of MCII: a reduction equal to or greater than 0.8, 1.4, and 1.2 seconds for the TUG; an increase equal to or greater than 0.2, 0.3, and 0.2 m/s for the 40-m SPWT; an increase equal to or greater than 2.0, 2.6, and 2.1 repetitions for the 30 CST; an increase equal to or greater than 5.0, 12.8, and 16.4 steps for the 20-cm step test. The variation in methods provided very different results. This illustrates the importance of comparing methodologies and reporting a range of values associated with the MCII, as such values vary, depending upon the methodology chosen.