Minimal Important Changes of Common Outcome Measures of Physical Function in Individuals With Knee Osteoarthritis: A Prospective Clinical Study.

Abstract

To investigate the minimal important change (MIC) for the 40-meter Fast Paced Walk Test (40m FPWT), 30-second Chair Stand Test (30s CST), 11-step Stair Climb Test (SCT), and Western Ontario and McMaster Universities Osteoarthritis Index - Physical Function subscale (WOMAC-PF) in individuals with knee osteoarthritis according to 3 methods described in the literature. A prospective clinical study. Department of Physiotherapy at the Federal University of São Carlos (Brazil). A total of one hundred and seven (N=107) participants. Not applicable. Performance-based tests and WOMAC-PF were applied. After 6 months, the Global Perceived Effect (GPE) scale was used to evaluate changes in physical function. A GPE cutoff score was established to categorize participants as improved or not improved. The MIC_mean, MIC_{receiver operating characteristic (ROC)}, and MIC_adjusted were calculated. Anchor reliability was assessed through longitudinal confirmatory factor analysis. Of the 80 study participants, 19 were in the improved group. The MIC_mean of the subgroups ranged from 0.07 to 0.29 m/s for the 40m FPWT, 2.07 to 5.29 stands for the 30s CST, 2.14 to 5.58 seconds for the 11-step SCT, and 4.21 to 27 for the WOMAC-PF. The MIC_ROC values were 0.14 m/s for the 40m FPWT, 1.5 stands for the 30s CST, 1.79 seconds for the 11-step SCT, and 4.5 for the WOMAC-PF. The MIC_adjusted values were 0.10 m/s for the 40m FPWT, 0.7 stands for the 30s CST, 4.0 seconds for the 11-step SCT, and 12.8 for the WOMAC-PF. The MIC_adjusted method considers both the proportion of improved patients and the reliability of transition ratings, making it preferable to MIC_mean and MIC_ROC. However, more high-quality studies are needed to assess its performance in samples with floor or ceiling effects.