Translation of questionnaires measuring health related quality of life is not standardized: a literature based research study.

Introduction: There is growing awareness of the need to explore patient reported outcomes in clinical trials. In the Scandinavian Surgical Outcomes Research Group we are conducting several clinical trials in cooperation between Danish and Swedish surgical researchers, and we use questionnaires aimed at patients from both countries. In relation to this and similar international cooperation, the validity and reliability of translated questionnaires are central aspects.

Main Objectives: The purpose of this study was to explore which methodological measures were used in studies reporting translation of questionnaires. Furthermore, we wanted to make some methodological suggestions for clinical researchers who are faced with having to translate a questionnaire.

Material And Methods: We designed a research study based on a survey of the literature and extracted data from published studies reporting the methodological process when translating questionnaires on health related quality of life for different diseases.

Results: We retrieved 187 studies and out of theses we included 52 studies. The psychometric properties of the translated versions were validated using different tests. The focus was on internal validity (96%), reliability (67%) criterion validity (81%), and construct validity (62%). For internal validity Cronbach's alpha was used in 94% of the studies.

Conclusions: This study shows that there seems to be a consensus regarding the translation process (especially for internal validity) although most researchers did not use a translation guide. Moreover, we recommended that clinical researchers should consider three steps covering the process of translation, the qualitative validation as well as the quantitative validation.