Screening men for aortic aneurysm

A national population screening service will be cost effective

Papers p 1135

Abdominal aortic aneurysm is a potentially lethal condition, much more common in older men, and, sadly, often first recognised only after rupture and death. Some 75% of patients die before arriving at hospital, and of the survivors, half make it to the operating theatre.1 The operative mortality for ruptured aneurysm remains about 40% at 30 days,2 compared with a mortality of 5-6% for elective surgery.3 Surely early ultrasound detection should be worth while. We now have the previously missing data to justify a national screening programme.

The Multicentre Aneurysm Screening Study Group reports the outcomes of aneurysm related mortality with health related quality of life and cost effectiveness. 4 5 The authors conclude that a single ultrasound scan in men aged 65 reduces aneurysm related deaths at acceptable cost. They put screening to the test in a population based randomised controlled trial of 70 000 men at four centres in the south of England, an area of relative social privilege. Randomisation was from general practitioners' lists—men in the “invited group” were offered screening and men in the control group were not. The authors applied the criteria of the UK small aneurysm trial, later adopted in the American trial, to the invited group. 3 6 Accordingly, surveillance was undertaken until the aneurysm reached 5.5 cm, grew more than 1 cm per year, or became tender. At that point, the patient was referred to a vascular surgeon, and surgery often followed unless the patient refused or was unfit.

Eighty per cent accepted screening, and 65 deaths related to aneurysm occurred in the invited group against 113 in the controls, an estimated risk reduction of 42%. Of the invited group 322 had elective operations compared with 92 in the controls, and mortality at 30 days was 6% for both groups. A total of 27 emergency procedures were undertaken in the invited group and 54 in the control group. The risk reduction was principally a result of reduced deaths from rupture in the invited group. This risk reduction was achieved with small but significant deterioration in health status measures in patients with aneurysms detected at screening.

Costs measured included screening, surveillance, and hospital costs of surgery and drugs. The mean cost for elective aneurysm repair was £6909 ($10 917; €10 819) and for emergency surgery, £11 176. After four years the cost effectiveness was £36 000 per quality adjusted life year gained, but this should fall to £8000 at 10 years, with 710 subjects being screened to prevent one death. This implies that screening would be cost effective in the long term. So the clinical and economic analyses of this trial, taken together with previous data to show the reliability of a single aortic ultrasound scan at age 65, can be used to justify screening for men. 4 5 7

Mortality from all causes was not a primary end point, because of numbers required; 11% died in each group by the end of the trial. But this throws the precision of diagnosis of aneurysm related mortality into the spotlight as this was used as the primary end point, representing merely 2% of deaths in the invited and 3% in the control group. An independent working party investigated potential aneurysm related deaths and sudden deaths. The trialists did their best, but all their recommendations hang on the reliability of this end point and the accuracy of death certificates.

Important questions remain. The presence of aortic aneurysm indicates an increased risk of cardiovascular death, so should patients with aneurysms detected at screening be prescribed statins or aspirin? Did the detection of aneurysms at screening alter the cardiovascular health care or lifestyle of the patients in the trial? If screening is to be effective an effective treatment needs to be used to stop the growth of the aneurysm. What about women? Scott and colleagues have implied that screening women is not worth while.8 Although aneurysms are less common in women, rupture is more frequent and occurs at a smaller aortic diameter.1 Leaving women out of a national screening programme might be controversial. When should patients be referred to a vascular surgeon? Will endovascular repair of the aneurysm make a difference?

Most vascular surgeons would like to see patients with aortic aneurysms detected at screening promptly, even though intervention should rarely be considered before the diameter exceeds 5.5 cm, and the rate of rupture of these small aneurysms is only 1% per year. 3 6 The first trials to compare endovascular with open aneurysm repair are due to report operative mortality in 2004 and early durability in 2005. No data support endovascular repair for smaller aneurysms.

For the moment the data support a national ultrasound screening programme for aortic aneurysm. The participants and sponsors of this trial are to be congratulated on a job well done. Now we should move forward to screening in a manner that increases the evidence base and answers some of the questions about cardiovascular health care and changes in life- style in those with aortic aneurysms detected at screening.