Cross-cultural adaptation and validation of Singapore English and Chinese versions of the Knee injury and Osteoarthritis Outcome Score (KOOS) in Asians with knee osteoarthritis in Singapore

OBJECTIVE: To cross-culturally adapt and validate Singapore English and Chinese versions of the Knee injury and Osteoarthritis Outcome Score (KOOS) in patients with knee osteoarthritis (OA) in Singapore. METHODS: Singapore English and Chinese versions were cross-culturally adapted from the source English KOOS following standard guidelines (including cognitive debriefing). Patients were asked to complete identical questionnaires containing the KOOS, Short Form 36 Health Survey, and EQ-5D twice within 6 days. Reliability was assessed using Cronbach's alpha and intraclass correlation coefficients (ICC), dimensionality using item-to-domain correlations and convergent and divergent construct validity using 14 and 13 a priori hypotheses, respectively. RESULTS: Singapore English and Chinese KOOS versions were well accepted by patients in pilot testing and were therefore administered to a consecutive sample of 127 English and 131 Chinese-speaking Singaporeans with knee OA. Cronbach's alpha exceeded 0.7 for all domains except for Chinese pain and symptoms domains. ICC exceeded 0.7 for all domains except for English sport and recreation and Chinese knee-related QoL domains. Hypothesized item-to-domain correlations (Spearman's rho>or=0.4) were observed for 38 items in English and 29 in Chinese versions. Convergent construct validity was supported by the presence of hypothesized moderate/strong correlations (rho=0.37-0.65) for 13 and 11 a priori hypotheses in the English and Chinese KOOS, respectively. Divergent construct validity was supported by the presence of weak correlations (rho=0.02-0.34) for 12 and 11 a priori hypotheses in the English and Chinese KOOS, respectively. CONCLUSION: The Singapore English and Chinese KOOS were well accepted and demonstrated acceptable reliability and validity in Asian patients with knee OA in Singapore.