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

OBJECTIVES

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.

DESIGN

A prospective clinical study.

SETTING

Department of Physiotherapy at the Federal University of São Carlos (Brazil).

PARTICIPANTS

A total of one hundred and seven (N=107) participants.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

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, MIC, and MIC were calculated. Anchor reliability was assessed through longitudinal confirmatory factor analysis.

RESULTS

Of the 80 study participants, 19 were in the improved group. The MIC 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 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 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.

CONCLUSIONS

The MIC method considers both the proportion of improved patients and the reliability of transition ratings, making it preferable to MIC and MIC. However, more high-quality studies are needed to assess its performance in samples with floor or ceiling effects.