The test-retest reliability and correlation of Thai version of the Western Ontario and McMaster Universities Osteoarthritis Index and pain scale in older people with knee osteoarthritis

The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is a standardized questionnaire that is widely the most use by health professionals for evaluate conditions of patient with knee osteoarthritis (OA). The 5-point Likert WOMAC was developed to use among older people with knee OA. Aim of this study was to estimate the test–retest reliability of Thai 5-point Likert version of WOMAC in older people with knee OA and correlation with visual analogue scale (VAS) pain. Thirty older people with symptomatic knee OA aged 50-85 years (average age 68.7±7.4 years) have live in Tumbon Sila, Muang district, Khon Kaen province. All subjects were completely asked to self-reported functional impairment the WOMAC form, 2 times with assistance of investigators. The WOMAC includes 3 dimensions in evaluating of pain, stiffness and physical functioning of the joints. Intraclass correlation coefficient (ICC) was used to describe the test- retest reliability.  The ICC of pain dimension = 0.75 (95% CI: 0.47 to 0.88), stiffness dimension = 0.59 (95% CI: 0.14 to 0.81), physical function dimension = 0.81 (95% CI: 0.60 to 0.91) and global = 0.86 (95% CI: 0.70 to 0.93). The significant correlation between WOMAC pain subscale and VAS was moderate (r = 0.43, p<0.05). The study concluded the Thai 5-point Likert version of WOMAC is a suitable tool for assessing knee OA in Thai elderly because of good reliable, low cost and timeless. In using WOMAC evaluated elderly people with OA in the future should consider other impact factors such as context and culture of community. Keywords: Knee osteoarthritis, Reliability, Correlation, WOMAC, VAS