AAA Rescreening Worthwhile in Dollars Per Life

Major Finding: For men with an initial aortic diameter of 25-29 mm, a single rescreening after 5 years would benefit 452 per 100,000 men. Lifetime screening every 5 years would benefit 794 per 100,000, but at a nearly threefold higher cost per QALY.

Data Source: Researchers used a decision analytical model to assess a hypothetical cohort of 65-year-old men from the general population, including ad hoc parameter estimates from the Danish Vascular Registry and other registries.

Disclosures: The study was funded by the Health Research Fund of Central Denmark Region and the Research Fund of Viborg Hospital. The researchers disclosed financial support from these two agencies, but no other relevant disclosures.



A new model demonstrated that at least one additional screening for abdominal aortic aneurysm was more cost effective in dollars per quality-adjusted life-year than was the single screening currently mandated for select populations in countries like the United States and England.

Previous decision models agreed that the optimal AAA screening protocol is a once-in-a-lifetime scan that is performed in men at age 65. However, none of these models examined the additional benefit of rescreening individuals whose aortic diameters approached but did not exceed the defined aneurysm threshold.

Dr. Rikke Søgaard and his colleagues developed their new model to determine if there was an optimal rescreening schedule for patients. They tested four screening strategies (no screening, once per lifetime screening, twice per lifetime screening with a 5-year interval, and lifetime screening every 5 years) for a hypothetical cohort of 100,000 men aged 65 years who were taken from the general population. Each individual was assigned to one of the four strategies. The researchers then compared the estimated lifetime costs and benefits of the four AAA strategies for this population.

The model used microsimulation of 6-month cycles to provide detailed epidemiologic results for each of the strategies, based on key events (detection, symptoms, rupture, and death) during a simulated lifetime. Apart from rupture rates taken from a systematic review, parameter estimates were the result of original analyses composed of a combination of research registries from two Danish screening trials, the Danish Vascular Registry, and national registries for causes of death.

Assuming a 12% per year incidental detection rate of aneurysms measuring 55 mm and larger, the model predicted that 2,469 men would be detected with a clinically relevant aneurysm. A single rescreening after 5 years of individuals without initial aneurysms who had an initial aortic diameter of 25-29 mm would detect an additional 452 men per 100,000 of those originally screened, whereas lifetime rescreening every 5 years thereafter would detect a total of 794 men with a clinically relevant aneurysm per 100,000.

Most of these aneurysms were smaller than the threshold for surgery, but appropriate for watchful waiting with rescreening, according to Dr. Søgaard of the University of Southern Denmark, Odense, and his colleagues.

The researchers found that elective surgeries would increase from 861 to 1,390 with a once-per-lifetime screening, to 1,496 for a single rescreening after 5 years, and to 1,530 with rescreening every 5 years for life. The rate of aneurysm-related mortality dropped with initial screening from 788 to 538 per 100,000, further falling to 520 and 511 for the single rescreening and the lifetime rescreening, respectively. "This decrease was the result of replacing acute surgery with elective surgery," the researchers stated (BMJ 2012 July 5 [doi:10.1136/bmj.e4276]).

The cost effectiveness of rescreening had not previously been studied, according to the authors. They determined that according to their model, there was a 92% probability that any rescreening protocol would be cost effective if it were at or below a threshold of £20,000 (24,790 euros and $31,460) per quality-adjusted life-year. They estimated that the incremental cost effectiveness was £10,013 per QALY, well under the threshold.

However, Dr. Søgaard and his colleagues also pointed out that substantial uncertainty surrounded this ratio, and "with an average incremental cost-effectiveness ratio of lifetime rescreening of £29,680, the optimal screening strategy is indeterminate"

"This study has policy relevance for two different scenarios. In Denmark, where no national guidance has been issued, it suggests that screening will be cost effective. In England and Scotland, where screening is currently being implemented (as is also the case in the United States), this study supports further consideration of rescreening, at least once," the researchers concluded.

The study was funded by the Health Research Fund of Central Denmark Region and the Research Fund of Viborg Hospital. The researchers disclosed financial support from these two agencies but no other relevant disclosures.

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