An economic evaluation of an abdominal aortic aneurysm screening program in Italy

Abstract

Abdominal aortic aneurysm (AAA) is defined as a localized dilatation of an aortic vessel. Though predominantly asymptomatic, it is a chronic degenerative condition associated with life-threatening risk of rupture. The early diagnosis of AAA, ie, before it ruptures, is therefore important; a simple, effective diagnostic method is ultrasound examination. To assess the benefit of screening in Italy, we developed a cost-effective Markov model comparing screening vs nonscreening scenarios. A 13-health-states Markov model was developed to compare two cohorts of 65- to 75-year-old men: the first group undergoing screening for AAA by means of ultrasound (US), the second following the current practice of incidental detection. The following health states were distinguished: no AAA, unknown small AAA (3-3.9 cm), followed-up small AAA (1 year), unknown medium-sized AAA (4-4.9 cm), followed-up medium-sized AAA (6 months), unknown large AAA (>5 cm), elective repair, emergency repair, postelective-repair AAA, postemergency-repair AAA, rejected large AAA, and death. Transitions between health states were simulated by using 6-month cycles. Transition probabilities were derived from a literature review of relevant randomized controlled trial and from a screening program that is currently ongoing at San Martino Hospital in Genoa, Italy. The Italian National Health Service (NHS) perspective was adopted and incremental cost per life-year saved was calculated with a lifetime horizon; costs and health benefits were discounted at an annual rate of 3% from year 2 onward. Uncertainty surrounding the model inputs was tested by means of univariate, multivariate, and probabilistic sensitivity analyses. Considering an attendance rate of 62%, the individual cost per invited subject was €60 (US $83.2); 0.011 additional quality adjusted life years (QALY) were gained per patient in the screened cohort, corresponding to an incremental cost-effectiveness ratio (ICER) of €5673/QALY (US $7870/QALY). The results were sensitive to some parameter variations but consistent with the base case scenario. They suggest that on the basis of a willingness-to-pay threshold of €50,000/QALY, screening for AAA is cost-effective, with a probability approaching 100%. As in economic evaluations developed in other countries, such as the UK, Canada, and The Netherlands, setting up a screening program for AAA can be considered cost-effective from the Italian NHS perspective.