Cross-cultural adaptation of the systemic lupus erythematosus quality of life questionnaire into Chinese

Objective. We have previously validated the English version of the Systemic Lupus Erythematosus Quality of Life Questionnaire (SLEQOL) in our patients with lupus. Many of our Chinese patients are not fluent in English and therefore a Chinese version (SLEQOL-C) has been adapted for their use. Methods. Two independent translators translated the SLEQOL into Chinese. A consensus version was derived from both sets of translations. Back translation of this version was performed by another 2 independent translators who had neither been involved in the forward translation nor encountered the SLEQOL. The final version, SLEQOL-C, was finalized after rectifying the discrepancies revealed by the back translation. Linguistic validity was tested in open interviews with bilingual patients with lupus. The SLEQOL-C and SLEQOL were administered to patients to determine whether they displayed differential item functioning (DIF). Results. In general, most of the items in English could be expressed in Chinese precisely, although a few instructions had to be altered slightly to make them more idiomatic. The forward and back translations of the SLEQOL were accomplished without major difficulties. A total of 638 patients were interviewed (62.8% with the SLEQOL and 37.2% with the SLEQOL-C). Using DIF analysis, there was no detectable test bias due to language use after controlling for repeated observations, age, sex, and ethnicity. Conclusion. The SLEQOL-C has semantic, idiomatic, and conceptual equivalence to the SLEQOL. The rigorous process of cross-cultural translation provides some measure of quality in the content validity.