Measuring health related quality of life in patients with rheumatoid arthritis--reliability, validity, and responsiveness of a Swedish version of RAQoL.

OBJECTIVE: To adapt the Rheumatoid Arthritis Quality of Life (RAQoL) questionnaire for Swedish patients and evaluate psychometric properties in a prospective study. METHODS: Reliability was assessed in 61 patients filling in RAQoL two times with one week's interval. 114 patients completed RAQoL and Nottingham Health Profile (NHP) on 2-3 occasions 6 months apart. Validity was evaluated comparing RAQoL-scores to disease-related variables and NHP subscales. Standardized response mean was applied to calculate responsiveness with the RA-related variables as external indicators of change. RESULTS: Test-retest reliability was high and internal consistency sufficient. RAQoL correlated as expected to NHP section scores. In a multivariate model the Stanford Health Assessment Questionnaire disability index (HAQ) and general health could explain 40% and disease activity measures 13% of the variance of RAQoL. Correlations between change scores of clinical variables and RAQoL and NHP were weak but positive. Standardized response means regarding change of disease activity, HAQ, and general health were small but in the same range for both RAQoL and NHP. CONCLUSION: The Swedish RAQoL had similar measurement properties as the original version. However, responsiveness regarding condition specific measures was not better than for the generic instrument NHP.