Quality of life assessment and screening tool development for endometriosis

The thesis is based on three papers on endometriosis, a relatively common chronic inflammatory gynecological disease which can cause significant pain and infertility. All three papers are based on cross-sectional data from postal surveys conducted among a randomly selected sample of women residing in Oslo and members of the Norwegian Endometriosis Association and the Oslo Rheumatoid Arthritis Registry. The main weakness of all three papers is possible selection bias. The aim of the first paper was to evaluate the measurement properties of the Norwegian version of the disease-specific quality of life questionnaire Endometriosis Health Profile-30. The scale self-image of the Norwegian version EHP-30 does not seem to measure the construct self-image appropriately. Thus, for Norwegian quality of life studies on women with endometriosis, the EHP-30 must be used with caution. The aim of the second paper was to compare quality of life in women with endometriosis and women with rheumatoid arthritis using the generic quality of life questionnaire Short form-36. Women with endometriosis seemed to have poorer mental quality of life compared with women with rheumatoid arthritis, despite similar pain scores. The aim of the third paper was to identify predictors of endometriosis among factors commonly associated with endometriosis and available to physicians through medical interview. Further, if successful, to combine these to develop and internally validate a prediction model to aid primary care physicians in early identification of women at high risk of developing endometriosis. The predictors absenteeism from school due to dysmenorrhea and family history of endometriosis demonstrated the strongest association with disease. A prediction model based on these two predictors appears to be a relatively efficient screening tool for endometriosis

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

Development of a prediction model to aid primary care physicians in early identification of women at high risk of developing endometriosis: cross-sectional study

To identify predictors of disease among a few factors commonly associated with endometriosis and if successful, to combine these to develop a prediction model to aid primary care physicians in early identification of women at high risk of developing endometriosis.Cross-sectional anonymous postal questionnaire study.Women aged 18–45 years recruited from the Norwegian Endometriosis Association and a random sample of women residing in Oslo, Norway.157 women with and 156 women without endometriosis.Main outcome measuresLogistic and least absolute shrinkage and selection operator (LASSO) regression analyses were performed with endometriosis as dependent variable. Predictors were identified and combined to develop a prediction model. The predictive ability of the model was evaluated by calculating the area under the receiver operating characteristic curve (AUC) and positive predictive values (PPVs) and negative predictive values (NPVs). To take into account the likelihood of skewed representativeness of the patient sample towards high symptom burden, we considered the hypothetical prevalences of endometriosis in the general population 0.1%, 0.5%, 1% and 2%.The predictors absenteeism from school due to dysmenorrhea and family history of endometriosis demonstrated the strongest association with disease. The model based on logistic regression (AUC 0.83) included these two predictors only, while the model based on LASSO regression (AUC 0.85) included two more: severe dysmenorrhea in adolescence and use of painkillers due to dysmenorrhea in adolescence. For the prevalences 0.1%, 0.5%, 1% and 2%, both models ascertained endometriosis with PPV equal to 2.0%, 9.4%, 17.2% and 29.6%, respectively. NPV was at least 98% for all values considered.External validation is needed before model implementation. Meanwhile, endometriosis should be considered a differential diagnosis in women with frequent absenteeism from school or work due to painful menstruations and positive family history of endometriosis