Measuring health status in British patients with rheumatoid arthritis: reliability, validity and responsiveness of the short form 36-item health survey (SF-36).

The objective was to assess the performance of the SF-36 health survey (SF-36) in a sample of patients with rheumatoid arthritis (RA) stratified by functional class. The eight SF-36 subscales and the two summary scales (the physical and mental component scales) were assessed for test retest reliability, construct validity and responsiveness to self-reported change in health. In 233 patients with RA, the SF-36 scales were: reliable (intra-class correlation coefficients 0.76-0.93); correlated with American College of Rheumatology (ACR) core disease activity measures [Spearman r = -0.12 (erythrocyte sedimentation rate) to -0.89 (Modified Health Assessment Questionnaire)]; and responsive to improvements in health (standardized response means 0.27-0.9). The distribution of scores on four of the eight subscales (physical function, role limitations physical, role limitations emotional and social function) was clearly non-Gaussian. Very marked floor effects were noted with the physical function scale, and both ceiling and floor effects with the other three subscales. The two SF-36 physical and mental component summary scales are reliable, valid and responsive measures of health status in patients with RA. Six of the eight subscales meet standards required for comparing groups of patients, and the physical function and general health scales may be suitable for monitoring individuals. The two scales measuring role limitations have poor measurement characteristics. The SF-36 pain and physical function scales may be suitable for use as patient self-assessed measures of pain and physical function within the ACR core disease activity set.

Measuring health-related quality of life in rheumatoid arthritis: validity, responsiveness and reliability of EuroQol (EQ-5D).

The EuroQol (EQ-5D) generic health index comprises a five-part questionnaire and a visual analogue self-rating scale. The questionnaire may be used as a health index to calculate a 'utility' value or as a health profile. The validity, reliability and responsiveness of EQ-5D were tested in 233 patients with rheumatoid arthritis stratified by functional class. EQ-5D demonstrated moderate to high correlations with measures of impairment and high correlations with disability measures. Stepwise regression models showed that EQ-5D utility values and visual analogue scores were explained best as a function of pain, disability, disease activity and mood (R2 approximately 70%), although other variables (side-effects, years of education) were required to explain the visual analogue scores. The EQ-5D health index and visual analogue scale are more responsive than any of the other measures, except pain and doctor-assessed disease activity. The reliability of the EQ-5D index and EQ-5D visual analogue scale is as good or better than that of all other instruments except the Health Assessment Questionnaire. Some patients with severe long-standing disease had health states which attracted utility values below zero, i.e. from a societal perspective they were regarded as being in states 'worse than death'. The practical and ethical implications of these utility valuations are discussed, and at present the utility values should be used and interpreted with caution. With this caveat, EQ-5D is simple to use, valid, responsive to change and sufficiently reliable for group comparisons. It is of potential use as an outcome measure in clinical trials, audit and health economic studies, but further work is required on its performance in other clinical contexts and on the interpretation of the utility values.