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Screening for abdominal aortic aneurysms in men: a Canadian perspective using Monte Carlo-based estimates.

OBJECTIVE
Recently generated randomized screening trial data have provided good evidence in favour of routine screening for abdominal aortic aneurysm (AAA) to reduce AAA-related deaths in men aged 65 years and older. We developed an economic model that assessed the incremental cost-utility of AAA screening to help decision makers judge the relevance of a national screening program in Canada.


METHODS
We constructed a 14 health state Markov model comparing 2 cohorts of 65-year-old men, where the first cohort was invited to attend screening for AAA using ultrasonography (US) and the second cohort followed the current practice of opportunistic detection. Lifetime outcomes included the life-years gained, AAA rupture avoided, AAA-related mortality, quality-adjusted life years (QALYs) and costs. Transition probabilities were derived from a systematic review of the literature, and a probabilistic sensitivity analysis was carried out to examine the effect of joint uncertainty in the variables of our analysis. The perspective adopted was that of the health care provider.


RESULTS
Invitations to attend screening produced an undiscounted gain in life expectancy of 0.049 years and a gain in discounted QALY of 0.019 for an estimated incremental lifetime cost of CAN$118. The estimated incremental cost-utility ratio was CAN$6194 per QALY gained (95% confidence interval [CI] 1892-10 837). The numbers needed to invite to attend screening, and the numbers needed to screen to prevent 1 AAA-related death were 187 (95% CI 130-292) and 137 (95% CI 85-213), respectively. The acceptability curve showed a greater than 95% probability of the program's being cost-effective, and the model was robust to changes in the values of key parameters within plausible ranges.


CONCLUSION
Our results support the economic viability of a national screening program for men reaching 65 years of age in Canada. More clinical studies are needed to define the role of screening in subgroups at high risk, especially in the female population.