Adaptation and validation of the Turkish version of the Rheumatoid Arthritis Quality of Life Scale

Objective The aim of this study was to adapt the Rheumatoid Arthritis Quality of Life (RAQoL) questionnaire for use in Turkey and to test its reliability and validity. Methods The translation process included the recent guidelines for cross-cultural adaptation. Reliability of the Turkish RAQoL was assessed by internal consistency and test-retest reliability, internal construct validity by Rasch analysis, and external construct validity by associations with impairments, disability, and general health status. Cross-cultural validity was tested through analysis of differential item functioning (DIF) by comparison with data from the UK version of the RAQoL. Results Reliability of the adapted version was good, with high internal consistency (Cronbach's alpha 0.95 and 0.96 at times I and 2, respectively) and test-retest reliability (Spearman's rho 0.874). Internal construct validity was confirmed by excellent fit to the Rasch model (mean item fit 0.236, SD 1.113) and external construct validity by expected associations. The DIF for culture was found in four items. Conclusions Adaptation of the RAQoL for use in Turkey was successful. The instrument can be used in both national and international studies for cross-cultural comparison with the UK, as long as adjustments are made for the few items displaying DIF for culture.