Development and validation of a short form of the valued life activities disability questionnaire for rheumatoid arthritis.

OBJECTIVE: To develop and validate a shortened version of the Valued Life Activities disability and accommodations scale (VLA) for individuals with rheumatoid arthritis (RA).
METHODS: To shorten the existing VLA measure, item response theory analyses were conducted using data from 449 patients with RA. Next, the resulting 14-item shortened version of the VLA scale (S-VLA) was evaluated by structured interviews among 20 RA patients. Lastly, the S-VLA was administered to 150 RA patients along with other measures, including the Health Assessment Questionnaire (HAQ) and Short Form 36 (SF-36). A random sample of 50 patients completed the S-VLA 2 weeks later to assess reliability. Item statistics were calculated to evaluate correlations between individual items and the S-VLA total score. Correlations between the S-VLA and other measures were used to evaluate validity.
RESULTS: Test-retest reliability was 0.91, while Cronbach's alpha for the S-VLA was 0.95. None of the 14 items was associated with improved alpha coefficients when omitted. All of the items were strongly correlated with the S-VLA total score. S-VLA scores were highly positively correlated with the HAQ (r = 0.81, P ≤ 0.001), patient-reported disease activity (r = 0.71, P ≤ 0.001), satisfaction with abilities (r = 0.82, P ≤ 0.001), and number of days with activity limitations (r = 0.65, P ≤ 0.001). In addition, as hypothesized, the S-VLA was inversely correlated with the SF-36 physical component summary score (r = -0.78, P ≤ 0.001) and the physical functioning (r = -0.80, P ≤ 0.001), role physical (r = -0.67, P ≤ 0.001), and social functioning (r = -0.72, P ≤ 0.001) subscales.
CONCLUSION: The S-VLA is a short, valid, and reliable instrument that may prove useful for monitoring disability among individuals with RA.