Stukenborg, George J.

Introduction: Intracranial aneurysm (IA) and abdominal aortic aneurysm (AAA) rupture carry high mortality (40% and 75% respectively) and substantial morbidity in survivors. Recent research suggests that IA and AAA share genetic risk in addition to environmental factors. Retrospective data from our institution identified a population harboring both IA and AAA and showed a high rupture rate for IA (44.2%). We previously demonstrated that screening for AAA in patients with IA is cost-effective based on estimated and published data. We hypothesize that screening for IA in patients with AAA is also cost-effective. Method: We developed a decision-making model using TreeAge Pro 2013 software assuming a hypothetical population with known AAA and truncated screening versus no screening for IA using magnetic resonance angiography. Based on IA size and location, patients were either treated endovascularly or placed on surveillance. Proportions, risks, utilities, and costs for each decision arm were derived from literature. Results: At a given rupture rate, incremental effectiveness varied linearly with coprevalence of AAA and IA. For an assumed rupture rate of 5%/year, screening was effective for coprevalence >6.8% (top graph) and was cost-effective for coprevalence >7.7%. The incremental cost-effectiveness ratio (ICER) favored screening (ICER=$54,193/QALY) at a 7.8% coprevalence and dropped to $27,841.50/QALY at 8.8% coprevalence. Our model was sensitive to IA rupture rate as well as coprevalence (bottom graph). Conclusion: Our model suggests the cost-effectiveness of screening for IA in patients with AAA, below the accepted societal threshold of an ICER $60,000/QALY at a coprevalence ≥7.8% and IA rupture rate ≥5%. These are plausible assumptions for this genetically high-risk population. Further prospective study is warranted to establish coprevalence of AAA and IA, rupture rates, and determine the benefit of dedicated screening.

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.