Lack of cross-cultural validity of the Endometriosis Health Profile-30

INTRODUCTION: The Endometriosis Health Profile-30 is a disease-specific patient-reported outcome measure of health-related quality of life. Cross-cultural validation of the Endometriosis Health Profile-30 has been performed for several translated versions. The aim of this study was to evaluate the measurement properties of a Norwegian version Endometriosis Health Profile-30. METHODS: This study was designed as a cross-sectional anonymous postal questionnaire study. A total of 157 women with endometriosis were included during a period from 2012 to 2013. Women aged 18–45 years were recruited from the Norwegian Endometriosis Association. Principal components analysis with varimax rotation was used to assess construct validity. Short Form-36 was used to determine convergent validity. Cronbach’s alpha was used to measure internal consistency. Intraclass correlation coefficients and paired t-tests were used to evaluate test–retest reliability. Floor and ceiling effects were estimated. RESULTS: Factor analysis resulted in a three and five-factor model for the core and modular questionnaire, respectively. Factor analysis could not support construct validity of the scales self-image and treatment. The Norwegian version Endometriosis Health Profile-30 demonstrated acceptable internal consistency and test–retest reliability, except for the scale relationship with children. Floor effects were observed for the scales self-image (20.1%), work life (33.9%), relationship with children (34.2%), and medical profession (20.5%). CONCLUSION: The construct self-image does not seem to be measured appropriately by the Norwegian version Endometriosis Health Profile-30, suggesting a lack of cross-cultural validity of the Endometriosis Health Profile-30. With multinational studies increasing, adequate translation, cross-cultural adaptation, and cross-cultural validation of instruments are essential to ensure equivalence in languages and cultures other than the original.