Expert opinion: screening for abdominal aortic aneurysm

There is good evidence for the efficacy of a targeted screening programme. By Mr Jonothan J Earnshaw

An estimated 6,000 men die every year in England and Wales after rupture of their abdominal aortic aneurysm (AAA). About 5 per cent of men aged 65 have an aortic aneurysm, defined as an aorta >3cm in diameter. Usually, the aneurysm remains small, but it has the potential to expand and rupture.

Rupture becomes increasingly likely if the aortic diameter is >5.5cm. Elective surgery can be carried out to replace the aorta with a synthetic tube through a laparotomy incision (open aneurysm repair). Alternatively, the aneurysm can be excluded from within by endovascular repair (EVAR), where a covered stent is inserted inside the aorta through groin incisions.

Surgery carries risks; the UK perioperative mortality rate is 2-7 per cent, but this compares favourably with the mortality rate of 85 per cent should the AAA rupture.

The case for aneurysm screening
A randomised controlled trial of aneurysm screening (the MASS trial) was carried out in the 1990s, involving some 70,000 subjects.1 Screening men reduced the rate of aneurysm-related deaths by almost 50 per cent. In meta-analysis of the available data, screening for AAA has been shown to be cost-effective in men in comparison with other screening investigations.2

In Gloucestershire, a model of population screening was established in 1991, which is likely to become the framework for a national programme. The model is based on mobile screening at the GP surgery for all men when they reach the age of 65.

The screening team visits each surgery in the county once a year and scans all that year's 65-year-old men, plus all men previously found to have a small aneurysm. Once the AAA reaches a significant size, the patient is referred to a vascular surgeon for treatment.

The Gloucestershire Aneurysm Screening Project has dramatically reduced the number of ruptured aneurysms in the county and focused resources on elective treatment.3 Operating earlier has reduced the elective mortality rate to <4 per cent in the past five years.

There is a clear process for introducing a national screening programme. The National Screening Committee (NSC) reviews all scientific evidence and makes a recommendation to the DoH. A working party of the NSC concerning aneurysm screening has spent the past few years assembling the data to justify AAA screening and has written a standard operating procedure.4

In April 2007, the NSC reported positively to the government on national screening and in January 2008, the prime minister endorsed the programme in a wide-ranging speech on medical screening in general. However, the details about the proposed programme remain sketchy.

It is acknowledged that vascular surgical services need some reorganisation, as does the availability of information for 65-year-old men before they decide to attend for screening. The Vascular Society of Great Britain and Ireland is very keen to support a national screening programme, and has agreed to review the delivery of quality vascular services.

Improving mortality rates after elective aortic surgery is thought to accompany increasing the number of procedures carried out by individual surgeons. There is a danger, however, that centralisation of vascular services may remove the availability of vascular surgery at district hospitals and leave smaller hospitals exposed. The solution may lie in joint working by vascular surgeons in networks consisting of several hospitals. Funding remains an area of concern. Ideally, the programme should be organised and funded centrally, so that it is delivered consistently and coherently across the country. Unfortunately, the current policy of moving funding to local level runs directly counter to this idea and risks the programme being introduced piecemeal. There is also the risk that national standards may not be accepted or adhered to. Details about funding will emerge over the next few months; the plan is to roll out the programme over five years. The first-wave networks will commence screening in 2008 (although these will largely be places that already have established local programmes).

Within Gloucestershire, AAA screening was strongly supported by GPs and their practices, where screening takes place. In more urban areas, there are other alternatives, such as mobile ultrasound screening units. There is also the opportunity for GPs to target a high-risk group of men with vascular disease for secondary prevention. For the programme to be effective, it will need the support of the entire medical community. A successful programme could prevent up to 3,000 premature deaths in England and Wales every year.

- Mr Jonothan J Earnshaw is consultant surgeon at the Gloucestershire Royal Hospital and honorary secretary of the Vascular Society of Great Britain and Ireland.

References
1. Kim LG, Scott RA, Ashton HA, Thompson SG, Multicentre Aneurysm Screening Study Group. A sustained mortality benefit from screening for abdominal aortic aneurysm. Ann Int Med 2007; 146: 699-706.
2. Cosford PA, Leng GC. Screening for abdominal aortic aneurysm. Cochrane Database of Systematic Reviews 2007, Issue 2. CD002945. DOI: 10.1002/14651858.CD002945.pub2
3. Earnshaw JJ, Shaw E, Whyman MR et al. Screening for abdominal aortic aneurysms in men. BMJ 2004; 328: 1122-4.
4. UK National Screening Committee - AAA Screening Working Group. Standard operating procedures for an abdominal aortic aneurysm (AAA) screening programme.


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