The 8-foot up and go test is the best way to assess physical function in the rheumatoid arthritis clinic

RA is characterized by poor physical function, which compromises patients' quality of life and outcome. Clinical assessment of function is usually performed using self-reported questionnaires, such as the Multi-Dimensional HAQ (MDHAQ) and the Short Form-36 (physical component) (SF36-PC). However, such subjective measures may not accurately reflect real functional status. This study aimed to determine: (i) which clinically practicable objective test best represents overall physical function; and (ii) the extent to which self-reported subjective functional measures reflect objectively assessed function.

Objective [isometric knee extensor strength, handgrip strength, sit-to-stands in 30 s, 8-foot up and go (8'UG), 50-foot walk (50'W) and estimated aerobic capacity (V̇O₂max)] and subjective (MDHAQ and SF36-PC) measures of function were correlated with one another to determine the best overall test of functional status in 82 well-controlled RA patients (DAS28 (s.d.) = 2.8 (1.0)).

In rank order of size, averaged correlations (r) to the other outcome measures were as follows: 8'UG: 0.650; 50'W: 0.636; isometric knee extensor strength: 0.502; handgrip strength: 0.449; sit-to-stands in 30 s: 0.432; and estimated V̇O₂max: 0.358. The MDHAQ was weakly (0.361) and the SF36-PC moderately correlated (0.415) with objective measures.

Our results show that the most appropriate measure of objective physical function in RA patients is the 8'UG, followed by the 50'W. We found discordance between objectively and subjectively measured function. In clinical practice, an objective measure that is simple and quick to perform, such as the 8'UG, is advocated for assessing real functional status.