Reliability and validity of the EnroQol in patients with osteoarthritis of the knee

Objective. To assess the reliability and validity of the EuroQol (EQ-5D) for osteoarthritis of the knee (OA knee). Methods. Eighty-two patients with OA knee were asked to complete on two occasions, separated by 1 week, the EQ-5D, the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index and the 36-item short form of the Medical Outcomes Study (SF-36). Results. In this patient population, < 10% of the 243 EQ-5D health states were active. The EQ-5D demonstrated a non-Gaussian distribution. Reliability [intraclass correlation coefficient (ICC) = 0.70] is acceptable for aggregate level data. There were significant rank correlations with both the WOMAC and SF-36. Conclusions. This study provides some evidence of EQ-5D construct validity and reliability. However, the restricted and non-normal distribution of scores, the marked difference between patients' self evaluation and derived societal utility tariffs, as well as the lack of discriminative ability for patients with 'moderate' morbidity within each of the five EQ-5D dimensions, are of concern.