The Performance and Association Between Patient-reported and Performance-based Measures of Physical Functioning in Research on Individuals with Arthritis.

OBJECTIVE

To evaluate the association between patient-reported outcome (PRO) and performance-based (PB) measures of physical functioning (PF) among individuals with self-identified arthritis to inform decisions of which to use when evaluating the effectiveness of a physical activity intervention.

METHODS

Secondary data analysis of a nonrandomized 2-arm pre-post community trial of 462 individuals who self-identified as having arthritis and participated in the Walk with Ease (WWE) intervention. Two PRO and 8 PB assessments were collected at baseline (preintervention) and at 6-week followup. We calculated correlations between PB and PRO measures, assessed how measures identified changes in PF from baseline to followup, and compared PRO and PB measures to arthritis symptoms of pain, stiffness, and fatigue.

RESULTS

Strength of correlations between PB and PRO measures varied depending on the PB measure, ranging from 0.21 to 0.54. PRO and PB measures identified PF improvements from baseline to followup, but none showed significant differences between the 2 WWE modalities (instructor-led or self-directed groups). Correlations with arthritis symptoms were stronger for PRO (0.30-0.46) than PB measures (0.03-0.31).

CONCLUSION

PRO measures may provide us with insights into aspects of PF that are not identified by PB measures alone. Use of PRO measures allows patients to communicate their perceptions of PF, which may provide a more accurate representation of overall PF. Our study does not suggest abandoning the use of PB measures to characterize PF in patients with self-identified arthritis, but recommends that PRO measures may serve as complementary or surrogate endpoints for some studies.