Contradictory findings enliven debate about value of AAA ultrasound screening

Two European studies published on the same day have reached opposite conclusions about the cost-effectiveness of ultrasound screening exams for abdominal aortic aneurysm.

Dr. Simon Thompson, director of the Medical Research Council Biostatistics Unit at the Institute of Public Health in Cambridge, United Kingdom, came to a positive conclusion about the exam's cost-effectiveness. His findings were based on nearly 70,000 subjects enrolled in the United UK Multicenter Aneurysm Screening Study (MASS).

Negative findings were reported from a collaboration involving Aarhus University, the University of Southern Denmark, and the Center for Public Health of Denmark's Central Region. Principal investigator Lars Ehlers used a mathematical model and data from the literature and the Danish Vascular Registry to estimate costs and outcomes for a hypothetical population of Danish men aged 65 from screening to death.

The National Health Service in England established a ultrasound-based screening program for men aged 65 to 75 in the spring 2008. Similar programs in Scotland and the U.S. have responded to evidence showing that screening and subsequent repair of large abdominal aortic aneurysms in this patient population leads to reduced AAA-specific mortality. According to the UK Office for National Statistics, about 6000 men die every year in England and Wales alone from ruptured aortic aneurysms.

 

From two years starting in 1997, Thompson and colleagues randomized patients aged 65 to 74 from four UK hospitals in two groups. One group received AAA ultrasound screening. The procedure was withheld from a second group that served as a control. Subjects were followed for an average of 10 years for information about morbidity, mortality, and the overall costs associated with aneurysm detection and treatment.

Investigators found that about half (155) as many subjects who were screened died from AAA than the 296 fatalities associated with the condition among control subjects. A cost-effectiveness analysis revealed that the benefits of screening improved over time, with cost per life year gained from about $67,299 after four years, $22,980 after seven years, and $12,475 after 10 years.

Findings also indicated that benefit of screening meant a progressive drop in aneurysm-related deaths by 42% at four years, 47% at seven, and 48% at 10 years. The cost/benefit calculation showed average per life year gains below the National Health Service's benchmark of £25,000 per life year gained for medical technologies and interventions.

Danish investigators found the estimated cost of screening per quality adjusted life year was more than $71,160, well beyond the local accepted benchmark of $49,530. The assessment did not match results from previous studies that claimed AAA screening is cost effective, investigators wrote.

"We believe our study provides a more realistic estimate of cost effectiveness (than the MASS study)," investigators wrote.

Both studies were published online 26 June in the British Medical Journal.

In an accompanying editorial, Martin J. Buxton, Ph.D., professor of health economics at Brunel University in Uxbridge, expressed confidence that the MASS study results are powerful enough to demonstrate the long-term effectiveness of screening. He supported continued financial and outcome monitoring to ensure screening remains cost-effective.

Buxton also criticized both groups for inadequately describing the underlying research model for their studies, and he asked the Danes for more financial data to explain why their costs were higher than those reported by the British.