BMJ  2008;336:862 (19 April), doi:10.1136/bmj.39517.443796.AD

Head to Head

Should we screen for abdominal aortic aneurysm? Yes

¹ Whipps Cross University Hospital, London E11 1NR

In January, the government announced five pilot screening programmes for aortic aneurysm in men aged 65 in England. Stephen Brearley describes the rationale for this proposal while James Johnson (doi: 10.1136/bmj.39514.494167.AD) argues that it is not without pitfalls

Around 5% of men aged between 65 and 74 have abdominal aortic aneurysms (maximum infrarenal aortic diameter of at least 3 cm).¹ The prevalence is some six times lower in women. Aneurysms expand inexorably² without causing symptoms until they rupture or the individual dies of another cause. When rupture occurs, barely half of the patients reach hospital alive.³ Of those who do, 40-60% do not survive to discharge, giving an overall mortality for ruptured aortic aneurysm in the region of 80%. Nearly 5000 people die of this condition each year in England and Wales.⁴

Some aneurysms are diagnosed before rupture occurs, but at present this is largely fortuitous. Conventional open repair of unruptured aneurysms below the renal arteries (95% of the total) carries a mean mortality of 9.5%,⁵ although recent UK series have reported mortalities of 5.5%, 6%, and 4.2%.^{2 5 6} Endovascular repair of aneurysms in the 60-70% of patients for whom this procedure is anatomically suitable carries a mortality of 1.6%.⁶ The advantage of having an aneurysm repaired before it ruptures is thus enormous.

Abdominal aortic aneurysms can be reliably detected by ultrasonography. The condition therefore fulfils admirably the criteria laid down by the UK National Screening Committee⁷: the condition is an important health problem, it can be readily detected by a simple test, and it can be treated much more effectively at the asymptomatic stage than once rupture has occurred.

Nevertheless, confounding factors may make screening programmes ineffective. These include poor uptake of invitations to be screened by elderly people and a higher than expected mortality from surgical treatment of screen detected aneurysms. A screening programme would certainly result in some people having surgery for aneurysms that would not have ruptured during their lifetime. There might be an adverse effect of the invitation to be screened, or of discovery of an aneurysm too small to require immediate treatment, on quality of life.

Evidence for screening

The UK screening committee based its decision to back screening programmes on the results of four randomised clinical trials: two in the UK,^{5 8} one in Western Australia,⁹ and one in Denmark.¹⁰ All but one (Chichester, UK) screened men only. The study populations ranged in age from 65 years to 73 (Denmark), 74 (UK multicentre aneurysm screening study (MASS)), 79 (Australia), or 80 (Chichester). Participants were randomised either to be invited for screening by ultrasonography or to no intervention. The principal end points were all cause mortality and aneurysm related mortality. Median follow-up in these trials now ranges from 43 months to 15 years.

Uptake of invitations to be screened ranged from 63% to 80% (80% for UK patients aged 65 to 74 years). Only one trial (Western Australia) showed a reduction in all cause mortality among patients invited for screening, something which none of them was powered to detect, but all four showed reductions in aneurysm related mortality ranging from 11% after 15 years median follow-up to 67% after 52 months (and the reduction was significant in the Danish and MASS trials).

A Cochrane review of aggregated data from these trials (which does not include recently published long term follow-up data) showed a small (5%) and non-significant reduction in all cause mortality among patients invited for screening but a highly significant reduction in aneurysm related mortality (odds ratio 0.60; 95% confidence interval 0.47 to 0.78).¹¹ The Chichester study reported a significant reduction in aneurysm rupture rates in the screening group (0.45; 0.21 to 0.99).

The MASS study reported a cost per life year gained of £28 000 (37 000; $56 000) after a median follow-up of 4.1 years. The authors estimated that this would fall to £8000 after 10 years’ follow-up. They recently published results derived from a median follow-up of seven years, which showed that the cost per life year gained had fallen to £12 342.

A national screening programme has the potential to prevent up to 2000 deaths a year in England and Wales from aneurysm related causes at a cost that is comparable to or below that achieved by other screening programmes. By screening all men just once, when they reach the age of 65, the cost will be reduced further with little loss of effectiveness. An economic analysis produced by the Centre for Reviews and Dissemination of the University of York in 2005¹² concluded that the likelihood of such a programme being cost effective was greater than 95%.

The US Preventive Services Task Force has reached similar conclusions about the value of screening to those of the UK committee. The Department of Health’s decision to establish pilot screening services in England and its intention to screen all 65 year old men within 10 years indicate that the argument for screening for abdominal aortic aneurysms has been won. Attention now needs to be focused on making the screening programme as efficient and effective as possible.

---

Competing interests: None declared.

References

1. Kim LG, Scott AP, Ashton HA, Thompson SG. A sustained mortality benefit from screening for abdominal aortic aneurysm. Ann Intern Med 2007;146:699-706.[Abstract/Free Full Text]
2. UK Small Aneurysm Trial Participants. Mortality results for randomised controlled trial of early elective surgery or ultrasonographic surveillance for small aortic aneurysms. Lancet 1998;352:1649-55.[CrossRef][Web of Science][Medline]
3. Bengtsson H, Bergqvist D. Ruptured abdominal aortic aneurysm: a population based study. J Vasc Surg 1993;18:74-80.[CrossRef][Web of Science][Medline]
4. Office for National Statistics. Mortality statistics. London: ONS, 2006.
5. Ashton HA, Buxton MJ, Day NE, Kim LG, Marteau TM, Scott RA, et al. The multicentre aneurysm screening study (MASS) into the effect of abdominal aortic aneurysm screening on mortality in men: a randomised controlled trial. Lancet 2002;360:1531-9.[CrossRef][Web of Science][Medline]
6. EVAR Trial Participants. Patient fitness and survival following abdominal aortic aneurysm repair: results from the UK EVAR trials. Br J Surg 2007;94:709-16.[CrossRef][Web of Science][Medline]
7. National Screening Committee. Criteria for appraising the viability, effectiveness and appropriateness of a screening programme. 2003. www.library.nhs.uk/screening.
8. Ashton HA, Gao L, Kim LG, Druce PS, Thompson SG, Scott RAP. Fifteen-year follow-up of a randomised clinical trial of ultrasonographic screening for abdominal aortic aneurysms. Br J Surg 2007;94:696-701.[CrossRef][Web of Science][Medline]
9. Norman PE, Jamrozik K, Lawrence-Brown MM, Le MT, Spencer CA, Tuohy RJ, et al. Population based randomised controlled trial on impact of screening on mortality from abdominal aortic aneurysm. BMJ 2004;329:1259-64.[Abstract/Free Full Text]
10. Lindholt JS, Juul S, Fasting H, Henneberg EW. Screening for abdominal aortic aneurysm: single centre randomised controlled trial. BMJ 2005;330:750-3.[Abstract/Free Full Text]
11. Cosford PA, Leng GC. Screening for abdominal aortic aneurysm. Cochrane Database Syst Rev 2007;(2):CD002945.
12. Henriksson M, Lundgren F. Decision-analytical model with lifetime estimation of costs and health outcomes for one-time screening for abdominal aortic aneurysm in 65-year-old men. Br J Surg 2005;92:976-83.[CrossRef][Web of Science][Medline]

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