To develop and validate a shortened version of the Valued Life Activities disability and accommodations scale (VLA) for individuals with rheumatoid arthritis (RA).
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.
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.
The S-VLA is a short, valid, and reliable instrument that may prove useful for monitoring disability among individuals with RA.