The Thai ICOAP-Hip: Cross-Cultural Adaptation and Validation for Assessing Intermittent and Constant Pain in Hip Osteoarthritis.

Background: The Intermittent and Constant Osteoarthritis Pain (ICOAP) questionnaire, developed by the OARSI/OMERACT initiative, is a tool for assessing pain in patients with hip and knee osteoarthritis. The aim of this study was to develop a Thai version of the ICOAP for hip through standardized translation and cross-cultural adaptation and to evaluate its reliability and validity.

Methods: In this prospective descriptive study, patients aged ≥18 years with hip osteoarthritis were enrolled. Thai Intermittent and Constant Osteoarthritis Pain for hip (ICOAP-Hip) was developed using a multilanguage translation and adaptation process. Forty-eight patients (24 men) completed the Thai ICOAP-Hip, pain subscale of the Thai Hip Osteoarthritis Outcome Score (HOOS), a Visual Analog Scale (VAS) for pain, and Thai Short Form-36 Health Survey version 2 (SF-36v2) during outpatient visits. Test-retest reliability was assessed by readministering ICOAP-Hip through telephone 48 hours later. Reliability was evaluated using the intraclass correlation coefficient (ICC) and Cronbach's alpha, while construct validity was examined using Pearson's correlation with comparator instruments.

Results: The Thai ICOAP-Hip total score showed excellent test-retest reliability (ICC = 0.988) and high internal consistency (Cronbach's α = 0.941). Construct validity was supported by strong negative correlations with the HOOS pain subscale (r = -0.737, P < 0.001) and SF-36v2 bodily pain subscale (r = -0.737, P < 0.001), as well as a strong positive correlation with VAS pain (r = 0.796, P < 0.001).

Conclusion: The Thai ICOAP-Hip is a reliable and valid instrument for evaluating pain in Thai patients with hip osteoarthritis.