Luke, Sothear H.

Introduction: Abdominal aortic aneurysm (AAA) rupture is associated with high mortality and morbidity. The U.S. Preventive Services Task Force recommends one-time ultrasound screening for AAA in men age 65-75 who have ever smoked. Little is known about other high-risk subpopulations. Recent linkage and genome-wide association studies confirm a shared genetic risk between AAA and intracranial aneurysms (IA). We tested the hypothesis that sonographic screening for AAA in individuals known to have IA is cost-effective. Methods: A decision tree model was developed to compare costs and outcomes of AAA screening compared to no screening in a hypothetical cohort of patients with IA. Event probabilities, utilities, and costs included in the model were derived through a comprehensive literature review. Expected outcomes of screening vs. no screening were measured in terms of quality-adjusted life years (QALY), lifetime costs and the overall cost-effectiveness ratio. Sensitivity analyses were performed to assess the effects of ranging baseline variables, within plausible minimum and maximum values, on model outcomes, as well as to identify thresholds of model variables where a decision alternative was dominated (both more expensive and less effective than the alternative). Results: In our base-case analysis, screening for AAA provided an additional 0.1055 QALYs (28.1521-screening, 28.0466-no screening) at an additional lifetime cost of $3.62 ($374.57-screening and $370.95-no screening). This yielded an incremental cost-effectiveness ratio (ICER) of $34.31/QALY. In sensitivity analyses, a prevalence of AAA in the IA population ≥ 7.5%, sensitivity of ultrasound screening ≥ 91%, or extrapolating the risk of AAA rupture to 6 years each caused the screening arm to dominate the model. Conclusion: Based on this model, screening for AAA in individuals with IA is cost-effective with an ICER of $34.31/QALY. This is well below accepted societal thresholds estimated to be less than $50,000/QALY. The sensitive variables in the model, particularly co-prevalence of IA and AAA, favored screening within conservative estimates from the literature. Prospective study evaluating the co-prevalence of IA and AAA will further elucidate the value of dedicated screening.