Screening for abdominal aortic aneurysms (AAA) is one of the most rigorously studied subjects in surgery.
Issues regarding what is classed as an aneurysm or when to intervene have been resolved by extensive clinical trails over many years.
The multicentre aneurysm screening study (MASS) reported in 2002 and was based on scanning almost 68,000 men. This addressed the cost effectiveness of screening in terms of cost per year of life saved. The figure was £36,000 in the first 3 years of screening and was predicted to fall to £8000 after screening had been in place for 10 years. In comparison, treatment with Herceptin for breast cancer costs £42,000 to £108,000 for each year of life saved. A year of life saved is the same whether due to screening or medication and this way of measuring the value of health spending allows comparison of value for money.
The Gloucestershire screening program reported on the results of 13 years of screening the at risk population of the whole of Gloucestershire in 2004. The authors state that screening abdominal aortic aneurysms with ultrasound fulfils all the criteria for a population screening program. They also go on to state:
Men with an aorta < 26 mm in diameter are reassured and discharged. Thus a single scan can largely rule out aneurysm disease for life in 95% of men. Those with an aorta of 26-39 mm are recalled annually for imaging in the surgery with the current year's 65 year old men (the screening intervals are under review). Men with an aorta ≥ 40 mm in diameter are referred to the outpatient clinic of one of Gloucestershire's four vascular surgeons. They have an ultrasound scan every six months because growth patterns become erratic as the aorta enlarges. If the aorta becomes over 55 mm in diameter, elective repair is considered.
This seems pretty unambiguous to me.
Operative mortality in the Gloucester study was 3% and said to be improving during the period of the study and also lower in patients picked up during screening. Contrast this with the 50% operative mortality of the 20% who survive long enough with a ruptured aneurysm to reach an operating theatre or the 5% annual mortality from ruptured aneurysm in patients with aneurysms of 55mm or larger.
These two studies have been accepted as sufficiently strong evidence for a national screening program in male past or current smokers aged 65-75 in the USA, Canada and the UK. The evidence is not sufficiently strong to recommend screening at other ages, in non-smokers or women though that has not stopped some private clinics recommending it. Aortascan - the private aortic aneurysm screening service in the UK - base their recommendation on the US Preventative Services Task Force analysis of the evidence. As treatment becomes safer and life expectancy increases it will probably be shown to be cost effective to screen other groups. Of course women and non-smokers die from aneurysms too and the cost-effective equation changes if people are willing to pay for their own screening.
Some doctors in the UK continue to argue against all the available evidence and deny their patients screening scans. It is understandable that the government would want to delay offering screening because they will not be able to offer it to the whole at risk group and, even if they could, they would be accused of sex and age discrimination because the science is too difficult for politicians to explain to the public in a sound bite and they would make more enemies than friends. However people in their 60s and 70s need to understand that the objections to aortic aneurysm screening are political not scientific.
About the Author
Consultant Radiologist & Partner
Hereford Radiology Group
Low cost private aortic aneurysm screening
Aortascan
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