A systematic review of instruments measuring foot function, foot pain, and foot-related disability in patients with rheumatoid arthritis

Objective. To compose an inventory of instruments that have been described to measure foot function (i.e., pressure and/or gait parameters), foot pain, and foot-related disability in rheumatoid arthritis (RA), and to investigate the clinimetric quality of these measures. Methods. A systematic search was conducted in Medline, CINAHL, EMBase, and Sportdiscus. Standardized criteria, extended with levels of evidence, were applied to assess the quality of the clinimetric studies and the properties (i.e., reliability, validity, and responsiveness) of the described instruments. Results. A variety of measurement instruments were identified. Only 16 instruments have been studied for their measurement properties in RA patients: 7 for assessing foot function, 3 for measuring foot-related disability, and 6 for measuring both foot pain and foot-related disability. Thirteen instruments were rated for reliability, of which 10 were rated positively on different levels of evidence. No positive rating for absolute measurement error was applicable for any of the tests. Internal consistency was reported for 7 instruments; 3 assigned a positive rating. For 2 instruments, Rasch analysis was used to assess the methodologic quality. A positive rating was reported for goodness-of-fit only, not for item calibration. Seven instruments were rated for construct validity, and 3 assigned a positive rating. Only 2 instruments were rated positively for responsiveness. Conclusion. This review offers a basis for choosing the most appropriate instruments for measuring foot function, foot pain, and foot-related disability in RA patients, both for clinical practice and for research. Further research on the quality of these measures is urgently needed.