Objective: To test the validity and reliability of a newly developed disease-specific multidimensional quality of life instrument: the Cedars-Sinai Health-Related Quality of Life Instrument (CSHQ-RA).
Methods: A total of 350 rheumatoid arthritis (RA) patients were asked to complete the CSHQ-RA at 2 time points (4 weeks apart). Patients also completed the Medical Outcomes Study Short Form 36 (SF-36) and the Stanford Health Assessment Questionnaire (HAQ) Disability Index (DI) at the second time point. Construct validity was tested, using Pearson's correlations, by comparing subscale scores on the CSHQ-RA to those obtained from the mental component summary (MCS) and physical component summary (PCS) of the SF-36. HAQ DI scores were used to assess the discriminant validity of the CSHQ-RA. Intraclass correlation coefficients (ICCs) were used to assess test-retest reliability.
Results: Response rates for the first and second survey were 83% (291) and 93% (276), respectively; 84% of respondents were women, and mean age was 57 years. Mean scores +/- SDs on instruments were: HAQ 0.73 +/- 0.69; MCS 49 +/- 12; and PCS 33 +/- 11. Pearson's correlations between the CSHQ-RA subscale scores and the SF-36 scores ranged from 0.55 to 0.76 (P < 0.001). Analysis of variance indicate that scores on the CSHQ-RA discriminated between levels of physical disability as measured by the HAQ (P < 0.001). Test-retest reliability was demonstrated in the instrument's subscale scores (ICC 0.70-0.90).
Conclusion: These results support the construct validity, discriminant validity, and reliability of the CSHQ-RA as a measure that captures the impact of RA on patients' health-related quality of life.