Validation and reliability of the Timed Up and Go test for measuring objective functional impairment in patients with long-standing rheumatoid arthritis: a cross-sectional study

Aim: This study aimed to validate the Timed Up and Go test (TUG) for measuring objective functional impairment in patients with established rheumatoid arthritis (RA) based on a prospective observational cohort of RA patients undergoing joint surgery. Methods: We collected data on demographics, Health Assessment Questionnaire Disability Index (HAQ-DI), and associations between TUG and HAQ-DI and other patient-reported outcomes, including European Quality of life scale (EQ-5D) were determined. Cut-off values of TUG for HAQ remission (HAQ-DI ≤0.5), normal HAQ (HAQ-DI ≤0.25), and the absence of disability in each HAQ-DI category were also determined by age. Results: A total of 435 patients were enrolled and analyzed. Mean age was 64.2 years, mean disease duration was 17.1 years, mean HAQ-DI was 1.14, and mean TUG was 11.1 sec. TUG was significantly correlated with aging, EQ-5D, and HAQ-DI categories related to lower limb function (arising, walking, reach and activity). After adjusting for age and sex, mean TUG values were 9.0 sec (95% CI, 7.7–10.3) in patients with HAQ remission and 8.7 sec (7.4–10.4) in those with normal HAQ. By age, mean TUG values for HAQ remission were 7.2 sec (5.9–8.5) in young patients (≤61 years), 9.1 sec (7.6–10.5) in middle-aged patients (62–70 years) and 10.0 sec (5.7–14.2) in old patients (≥71 years). Conclusion: TUG was significantly associated with functional impairment and aging in patients with long-standing RA. Thus, TUG could be useful in setting treatment goals for joint surgery and rehabilitation in established RA patients.