Cross-cultural validation of the ICOAP, physical function short forms of the HOOS, KOOS in patients with hip and knee osteoarthritis

Abstract

Background: The Intermittent and Constant Osteoarthritis Pain (ICOAP) was developed to comprehensively assess characteristics of pain. Physical Function short-forms for the Hip Injury and Osteoarthritis Outcome Score and Knee injury and Osteoarthritis Outcome Score (HOOS-PS and KOOSPS) were developed to improve feasibility and reduce item redundancy in the full versions of the Physical function scales of the HOOS and KOOS. Cross-cultural adaptation and validation of patient-reported outcome measures (PRO) are necessary in order to obtain results that are globally meaningful and comparable. Preliminary work from several countries has supported the reliability and validity of the ICOAP, HOOS-PS, and KOOS-PS. However, these studies conducted in different countries do not assess whether the relationships amongst measures are consistent across the different translated versions (i.e. as each language version was tested individually against the English version). In context of a multi-centre trial, it is important to ensure construct validity of the translated measures not only between two countries but across countries. Purpose: To evaluate the internal consistency and construct validity of the Physical Function short-forms for the Hip and Knee Injury Osteoarthritis Outcome Scores (HOOS-PS/KOOS-PS) and the Intermittent and Constant Osteoarthritis Pain (ICOAP) in a nine country study of patients consulting for total hip or knee replacement (THR or TKR). Methods: Patients completed HOOS-PS or KOOS-PS, ICOAP and Western Ontario and McMaster Universities' Osteoarthritis Index (WOMAC) pain and physical function subscales at their consultation visit. Internal consistency was calculated using Cronbach's alpha. The association of HOOS-PS/KOOS-PS and ICOAP with WOMAC pain and function subscales was calculated with Spearman correlation coefficients with95%confidence intervals. Finally, WOMAC pain and function scores were regressed on the interaction of the measure (HOOS-PS/KOOS-PS or ICOAP) and country to determine whether the associations differed across countries. Australia was used as the reference category. Results: HOOS-PS/KOO-PS and ICOAP demonstrated high internal consistency across countries (alpha 0.75-0.96 (hip) and 0.76-0.95 (knee)). Both HOOS-PS and KOOSPS demonstrated high correlations (0.76-0.90 and 0.75-0.91 respectively) with WOMAC function in all countries. ICOAP exhibited moderate to high correlations with WOMAC pain and function subscales (0.53-0.84 (hip) and 0.43-0.84 (knee)). Country by measure interaction terms revealed small effects for both the hip and knee. For the hip, therewas a maximum 0.27/100 point difference by country (for Germany) for the HOOS-PS and ICOAP with the WOMAC subscales. Using this example of the interaction of Germany by intermittent ICOAP pain score with the WOMAC pain, it meant that for each 0.27 decrease in the intermittent ICOAP pain score for the German participant, an Australian participant had a 1 point decrease in their WOMAC pain score. For the knee, this difference was a 0.28/100 point difference. Conclusion(s): The results of this study support the crosscultural validity and internal consistency of the HOOS-PS, KOOS-PS, and ICOAP measures in patients with hip/knee osteoarthritis. Implications: This study presents a novel statistical approach in understanding whether the relationships among the translated versions of the measures are similar irrespective of the country. This approach can be incorporated in future to conduct cross-cultural validation of other measures.