Background: In interview studies, men under surveillance for screening-detected abdominal aortic aneurysms have reported ambivalence towards this diagnosis: the knowledge was welcomed together with worries, feelings of anxiety and existential thoughts about life's fragility and mortality due to the diagnosis. Previous surveys about health-related quality of life aspects among men under surveillance for screening-detected aneurysm have all used generic patient-reported outcomes. Therefore, the aim of this study was to extend the core-questionnaire Consequences of Screening for use in abdominal aortic aneurysm screening by testing for comprehension, content coverage, dimensionality, and reliability.
Methods: In interviews, the suitability, content coverage, and relevance of the core-questionnaire Consequences of Screening were tested on men under surveillance for a screeningdetected abdominal aortic aneurysm. The results were thematically analysed to identify the key consequences of abnormal screening results. Item Response Theory and Classical Test Theory were used to analyse data. Dimensionality, differential item functioning, local response dependency and reliability were established by item analysis, examining the fit between item responses and Rasch models.
Results: The core-questionnaire Consequences of Screening was found to be relevant for men offered regular follow-up of an asymptomatic screening-detected abdominal aortic aneurysm.Fourteen themes especially relevant for men diagnosed with a screening-detected abdominal aortic aneurysm were extracted from the interviews: 'Uncertainty about the result of the ultra sound examination', 'Change in body perception', 'Guilt', 'Fear and powerlessness', 'Negative experiences from the examination', 'Emotional reactions', 'Change in lifestyle', 'Better not knowing', 'Fear of rupture', 'Sexuality', 'Information', 'Stigmatised', 'Self-blame for smoking', 'Still regretful smoking'. Altogether, 55 new items were generated: 3 were single items and 13 were only relevant for former or current smokers. 51 of the 52 items belonging to a theme were confirmed to fit Rasch models measuring fourteen different constructs. No differential item functioning and only minor local dependency was revealed between some of the 51 items.
Conclusions: The reliability and the dimensionality of a condition-specific measure with high content validity for men under surveillance for a screening-detected abdominal aortic aneurysm have been demonstrated. This new questionnaire called COS-AAA covers in two parts the psychosocial experience in abdominal aortic aneurysm screening.