Objective: To compare validity, reliability, and responsiveness of generic and disease specific health-related quality of life (HRQOL) instruments in rheumatoid arthritis (RA).
Methods: Two samples of patients completed the Medical Outcomes Study Short Form-36 Health Survey (SF-36), EuroQol (EQ)-5D, 15D, Rheumatoid Arthritis Quality of Life Scale (RAQoL), Health Assessment Questionnaire (HAQ), and visual analog scales (VAS) for pain, fatigue, and global RA. VALIDITY (convergent, discriminant, and known-groups) was evaluated in a cross-section of 200 patients. Reliability was evaluated by agreement (intraclass correlation coefficient; baseline to 2 weeks) and internal consistency (Cronbach's alpha); and responsiveness by the standardized response mean stratified on improvement, status quo, or deterioration in health status after 6 months in 150 patients followed longitudinally. Followup questionnaires (at 2 weeks and 6 months) included questions about changes in health status since baseline.
Results: The cross-sectional sample included 77% women, median age 57 years (range 19-87), disease duration 6 years (0-58), with Disease Activity Score 28-joint count (DAS28) of 3.10 (1.21-6.47). The longitudinal sample included 80% women, median age 60 years (22-82).
Validity: all instruments discriminated between low, moderate, and high DAS28. Reliability: RAQoL and HAQ displayed good repeatability (ICC > 0.95) and internal consistency (Cronbach's alpha > 0.90). Responsiveness: SF-36 bodily pain scale and VAS pain were responsive to both improvement and deterioration.
Conclusion: All instruments were valid measures for HRQOL in RA. The RAQoL and HAQ displayed the best reliability, while the SF-36 bodily pain scale and VAS pain were the most responsive. The choice of instrument should depend on the study objectives.