Validation of the Western Ontario and McMaster University Osteoarthritis Index in Asians with osteoarthritis in Singapore

Objective: To assess the reliability and validity of the Western Ontario an d McMaster University, Osteoarthritis Index (WOMAC) as an outcome measure i n Asian patients with knee or hip osteoarthritis (OA) in Singapore. Design: The WOMAC was administered twice 7 days apart to 66 consecutive Eng lish-speaking Chinese, Malay or Indian Inpatients and outpatients with knee or hip OA seen at a tertiary referral centre through a structured intervie w, which also assessed demographic and other characteristics. Internal cons istency was assessed using Cronbach's alpha, reliability using Spearman's c orrelations, intraclass correlations and repeatability coefficients, and re lationships between WOMAC domains and known determinants of function using Spearman's correlations and the Mann-Whitney U-test. Results: The WOMAC showed good internal consistency (alpha =0.70 to 0.93) a nd good reliability, with intraclass correlations of 0.83 to 0.90 and mean test-retest score differences of 0.02 to 0.13 points (possible range 4 poin ts). Results of Likert scoring assessment supported the validity of the WOM AC when interpreted in the context of the close association between pain an d physical function. Eight of nine a prior! hypotheses relating WOMAC Pain and Physical Function scores to known determinants of function were present , supporting construct validity of this scale. Conclusion: The WOMAC Is a valid and reliable outcome measure in Asian pati ents with OA in Singapore. (C) 2001 OsteoArthritis Research Society Interna tional.