Psychometric evaluation of the Swedish version of the 30-item endometriosis health profile (EHP-30)

Background: The 30-Item Endometriosis Health Profile (EHP-30) is a specific instrument measuring quality of life among women with endometriosis. Although the Swedish version of EHP-30 is widely used in research and clinical settings, it has not yet been evaluated psychometrically. Ensuring validity and reliability is of most importance when using translated instruments. Therefore, the aim of the study was to evaluate the psychometric properties of the Swedish version of the EHP-30. Methods: This study was conducted at a Swedish referral university hospital specializing in endometriosis. Data collection was performed in January 2013. The EHP-30 was sent to 369 randomly selected women with a laparoscopy-verified endometriosis diagnosis. The psychometric evaluation included evaluation of data completeness, score distributions, floor and ceiling effects, internal consistency, factor analysis and test-retest reliability. Results: Out of the 211 women with endometriosis who answered the questionnaire, 128 were native Swedish speakers who had experienced symptoms of endometriosis during the past 4 weeks, and were included in the psychometric evaluation. Data completeness was 99.5%. The highest median score was found in the Control and Powerlessness subscale, and lowest in Pain. Distributions towards ill health were found in all subscales except for the pain subscale, but there were no noteworthy floor or ceiling effects. Internal consistency was good (Cronbach's alpha 0.83-0.96). Factor analysis could roughly confirm three of the five subscales. The test-rest analysis showed good reliability. Scores were systematically lower during the second measurement. Conclusions: We conclude that the Swedish version of EHP-30 is a valid and reliable instrument to measure health-related quality of life in women with endometriosis. It is understandable, acceptable and usable and can be recommended for use in clinical daily routines and for research purposes