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

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.

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.

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).

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