Screening for abdominal aortic aneurysms
The possibility of introducing a screening programme for abdominal aortic aneurysms (AAAs) in the UK has been considered for some time and plans have now been made to start this. It will join existing programmes, such as national screening for breast cancer.
Who will be screened?
In order for a screening programme for any condition to be justified as a reasonable use of taxpayers’ money, there needs to be good evidence that there is a particular group of people in whom the condition occurs frequently enough to make screening worthwhile.
In the case of aortic aneurysms that group is men aged 65 to 70, among whom about 2 per cent (1 in 50) have dilated aortas. Aortic aneurysms are much less common in women. The plan is for screening of all men when they reach the age of 65.
What will the test be?
There needs to be a practical test that will reliably detect the condition. In the case of AAAs ultrasound scanning by a skilled operator provides a quick and reliable test.
The test needs to be acceptable to people, so that most of them will attend. Large studies – especially ones based in Chichester and Gloucester – have shown that a high attendance rate is possible.
There needs to be a well-proven and effective treatment, with a good safety record. Open operations for aortic aneurysms have become increasingly safe over the years and the introduction of EVAR for suitable patients offers a treatment with still lower risks of complications.
The condition needs to be detected by screening at a stage when it can be treated effectively (this is especially important when screening for cancers). No matter what size an aortic aneurysm has reached when it is detected, treatment is usually possible.
The screening programme appears to be cost effective, by the usual standards of the National Health Service, in terms of saving life of good quality.
The evidence for all these requirements is now considered sufficiently good for a screening programme to be introduced for AAAs. It will be based on screening population areas of about 800,000 people and will come into operation area by area from 2008.
How will screening be offered?
All men will be offered screening when they reach their sixty-fifth birthday. Men will be identified through primary care (general practitioner) lists of patients. They will be invited to attend for a single scan. If this shows an aorta of normal size (less than 3 cm diameter) then no further scans will be done, because all the evidence suggests that the risk of ever developing an aneurysm is very small.
What will happen to patients with aneurysms detected by screening?
If the aorta is mildly dilated, further scans will be offered over the years, together with full explanation of the results. If an aneurysm of 5 cm diameter or greater is found, arrangements will be made for consultation with a vascular surgeon.
It is important to remember that very many aortas that are wider than 3 cm never expand to a size at which treatment needs to be considered. This is described in an earlier section.
What about the risks of treatment?
These are fully described in an earlier section and will obviously worry men with aneurysms detected by screening who are facing the possibility of treatment.
However, these men will in general be younger, fitter, and therefore less likely to suffer serious complications after treatment than patients who have had treatment in the past for aortic aneurysms that were discovered by chance.
The risks of death from treatment of aneurysms detected by screening is around one to two per cent for open operations and probably less than one per cent if EVAR is possible.
The long-term effects of the screening programme
As more and more men are screened for aortic aneurysms after the age of 65 so the number of undetected aneurysms in the ageing population will gradually decrease. This means that, within a few years, there are likely to be fewer operations for ruptured aortic aneurysms and fewer deaths as a result of aneurysms rupturing.
