Validação da versão curta do Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) para o português do Brasil

Abstract

Objective: To verify the clinimetric properties and validate the short version of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) in Brazilian Portuguese in individuals with knee OA. Materials and methods: The research was carried out at the integrated health outpatient clinics of the Universidade Nove de Julho (São Paulo, SP, Brazil), and was approved by the Research Ethics Committee of the same institution. The validation process was carried out following the principles of COSMIN, including individuals of both genders who have: Brazilian Portuguese as their mother tongue; age >40 years; knee pain ≥3 (0-10) for ≥12 weeks; morning stiffness; knee x-ray showing signs of knee OA; physician-defined diagnosis of knee OA. The psychometric properties evaluated were: test-retest reliability using the intraclass correlation coefficient (ICC), measurement standard error (SEM) and the minimum detectable difference (MDC); internal consistency, using Cronbach's alpha; construct validity using Spearman's correlation coefficient, analyzing the correlation magnitude of the short version of the WOMAC with the International Knee Documentation Committee (IKDC), the Medical Outcome Study 36 – Item Short-Form Health Survey (SF-36) and Numerical Pain Scale (END) and criterion validity analyzing the correlation of the short version with the long version of the WOMAC; the ceiling and floor effects. Results: 103 subjects with knee OA were included for validity analysis, and a subsample of 53 subjects was used for test-retest reliability. Adequate reliability and internal consistency were observed with the value of ICC ≥ 0.76, SEM ≤ 1.85, MDC ≥ 5.1 and Cronbach's alpha ≥ 0.84. With regard to construct validity, correlations greater than 0.50 were observed with the IKDC, END and the functional domains of the SF-36. The short version of the WOMAC presented a correlation > 0.70 with the long version and did not show ceiling and floor effects. Conclusion: The short version of the WOMAC knee has adequate measurement properties to analyze pain and physical function in Brazilian individuals with knee osteoarthritis.