Wednesday, 6 March 2013

UK Screening / Abdominal aortic aneurysm screening

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Screening in the UK 2011-12: Policy Review
One adult screening that has been introduced is the 

NHS Abdominal Aortic Aneurysm Screening Programme.

The NHS Abdominal Aortic Aneurysm Screening Programme (NAAASP) aims to reduce
the rate of premature death from ruptured aneurysms by up to 50% in men aged 65
and older. Men are offered an ultrasound scan in their 65th year while older men can
self-refer. Screening aims to reduce deaths by detecting abdominal aortic aneurysm (AAA) early
and offering appropriate surveillance or treatment, usually surgery.

Screening in England 2011-12

  • More than 100,000 men were screened for abdominal aortic aneurysm
  • An estimated 5,000 people in England die every year from ruptured abdominal aortic aneurysms. The programme aims to halve the number of premature deaths from aneurysm rupture amongst men aged 65 and over and has screened 107,000 65-year-old men this year. More than 1,600 [1.5%] were identified as having an aneurysm requiring surveillance or possible treatment. Once the programme has been running for 10 years we expect to have reduced the deaths of men from sudden rupture of the aneurysm by half. That is around 2,000 premature deaths prevented per year. (page 5)

Case study: positive screening tests can lead to difficult choices

Men who have a large aneurysm (5.5cm or larger) detected by the Abdominal Aortic
Aneurysm programme often have to decide not only whether to have it surgically repaired
but also what type of operation to have.

Tony Seccull felt fit and healthy when he was invited for screening but was told that he had a
large aneurysm 5.8cm wide. Tony was referred to vascular surgeon David Durrans to discuss
treatment options. Mr Durrans explained that Tony faced a risk of about one in 10 that his
aneurysm would rupture in the next 12 months. However, aneurysm repair, like all operations,
also carries some risk and around 2% of patients die following surgery. There are two main
aneurysm repair techniques: open surgery and endovascular repair, although not all patients or
all aneurysms are suitable for both.

“I decided I wanted it repaired as soon as possible because I didn’t want it hanging over me,”
said Tony. “Mr Durrans didn’t sell either option but outlined the pros and cons of both and
said it was my decision. I am very glad I was screened because without screening I would not
have been aware of the aneurysm and it could have failed on me at any time. I am also glad I
had the open surgery, even though the recovery is longer, because hopefully it will last for the
rest of my life.” (page 24)

abdominal aortic aneurysm screening

“It is estimated that abdominal aortic aneurysm screening should halve the number of premature deaths from aneurysm ruptures amongst men aged 65 to 74.” Mike Harris, Abdominal Aortic Aneurysm programme

An abdominal aortic aneurysm (AAA) usually produces no symptoms. So most people do not know they have one unless it ruptures (the walls of the blood vessel suddenly tear). A ruptured AAA is a surgical emergency that is fatal in around 80% of cases. In contrast, planned surgery to repair a large aneurysm detected by screening is successful in around 97- 98% of cases. Evidence suggests that up to 2,000 premature deaths from AAA rupture per year will be prevented in 10 years of running the programme. (page 28)

Abdominal aortic aneurysm screening has completely transformed vascular surgery in England. The key was specifying that services were only allowed to offer offer screening if they provided surgery in fewer, larger centres with more experienced surgeons. Previously many people were seen by general surgeons in smaller settings. By bringing expertise together in larger centres, this has improved outcomes and given vascular services a tremendous professional boost.” Robert Sherriff, UK NSC (page 29)

AAA Policy Database

Evidence Supporting the Policy

Screening for abdominal aortic aneurysm, a systematic review in the Cochrane Library Issue 2 2007. See Cosford PA, Leng GC. Screening for abdominal aortic aneurysm. Cochrane Database of Systematic Reviews 2007, issue 2.

... The likelihood of rupture depends on the size of the aneurysm. In the five years following diagnosis rupture occurs in approximately 2% of aneurysms found to be less than 4 cm in diameter and in over 25% of aneurysms larger than 5 cm (Ernst 1993). On this basis currently accepted practice for identified aneurysms is the following (Ballard 1999): • elective surgical repair for large aneurysms, usually taken to be 5.5 cm diameter or larger; • regular (e.g. six monthly) ultrasound surveillance for aneurysms below 5.5 cm diameter, with referral for surgery if the aneurysm grows at >1.0 cm per year or reaches 5.5 cm.

Screening for abdominal aortic aneurysm

An aneurysm is a localised widening (dilation) of an artery. The blood vessel can burst (rupture) because the vessel wall is weakened. Some 5% to 10% of men aged between 65 and 79 years have an abdominal aneurysm in the area of the aorta, the main artery from the heart as it passes through the abdomen. Abdominal aortic aneurysms are often asymptomatic but a rupture is a surgical emergency and often leads to death. An aneurysm larger than 5 cm carries a high risk of rupture. Smaller aneurysms are monitored regularly using ultrasound to see if they are becoming larger. Elective surgical repair of aortic aneurysms aims to prevent death from rupture. The incidence of aortic aneurysm in women as they age is lower than for men.
This review identified four controlled trials involving 127,891 men and 9342 women who were randomly assigned to aortic aneurysm screening using ultrasound or no screening. Only one trial included women. Two of the trials were conducted in the UK, one in Denmark and one in Australia. The results provide evidence of a benefit from screening in men with a strongly significant reduction in deaths from abdominal aortic aneurysm. The odds ratio (OR) for death was 0.60 (range 0.47 to 0.78, three trials) in men aged 65 to 83 years but was not reduced for women. From one trial there was also a decreased incidence of ruptured aneurysm in men but not women.
All-cause mortality was not significantly different between screened and unscreened groups some three to five years after screening, which is to be expected given the relative infrequency of abdominal aortic aneurysm as a cause of death.
Men who had been screened underwent more surgery for abdominal aortic aneurysm (OR 2.03; range 1.59 to 2.59, four trials) but resource analysis appears to demonstrate overall cost effectiveness of screening. There were no data on life expectancy, complications of surgery or quality of life.

A systematic review on screening for abdominal aortic aneurysm, produced by the U.S. Preventive Services Task Force examines the evidence. See:Screening for abdominal aortic aneurysm: a best-evidence systematic review for the U.S. Preventive Services Task Force (2005)

A randomised controlled trial into the effect of abdominal aortic aneurysm screening on mortality in men. See: The Multicentre Aneurysm Screening Study (MASS). Lancet 2002 Nov 16;360(9345):1531-9. PubMed abstract

Related documents

AAA policy review summary (Nov 2005) (PDF document, 80KB, 03/06/11)
Recommendation Screening of men aged 65, with the offer of a single test being made at that age, can be recommended in principle as a programme that meets the criteria and standards of the National Screening Committee.  It is recommended that a programme should start with men aged 65 and would not attempt to recruit men over the age of 65, although an individual over the age of 65 who requested screening would be eligible to be offered a test. It is not recommended that the test be offered to women at present because the mortality from ruptured abdominal aortic aneurysm is at present low.

External review against UK NSC criteria (PDF document, 133KB, 03/06/11)
Rupture of an aneurysm in the abdominal aorta caused about 6,800 deaths in England and Wales in the year 2000, the great majority in men because the age-specific prevalence of the condition is six times greater in men than in women. In men older than 65 years rupture of an abdominal aneurysm is responsible for 2.1% of all deaths and the overall mortality from rupture is between 65% and 85%.

Aneurysms of the abdominal aorta do not regress and are without symptom until they rupture. The mortality rate from aneurysm rupture is due not only to the severity of the injury but also to the speed of its evolution. Of all the deaths attributed to ruptured aneurysms, about half take place before the patient reaches hospital, and of those who reach hospital the mortality rate for emergency treatment is between 30% and 75%.

The cause of abdominal aortic aneurysm is not understood and primary prevention is not possible. As with other vascular diseases efforts to prevent people smoking or to help them stop smoking will influence risk but there are many other reasons to advocate smoking cessation, and at present abdominal aortic aneurysm can be regarded as a disease that cannot be prevented.

21. Public pressure for widening the eligibility criteria, etc, should be anticipated: Screening women is less common. The Chichester study demonstrated no benefit in a randomised trial of 9342 women (published in BJS 2002). Evidence is available on the low prevalence of AAA in younger men and its effect on cost and benefit.



In the United Kingdom the rate of AAA in Caucasian men older than 65 years is about 4.7%[68]
There are 15,000 deaths yearly in the U.S. secondary to AAA rupture.[69] The frequency varies strongly between males and females. The peak incidence is among males around 70 years of age, the prevalence among males over 60 years totals 2-6%. The frequency is much higher in smokers than in non-smokers (8:1), and the risk decreases slowly after smoking cessation.[70] Other risk factors include hypertension and male sex.[8] In the U.S., the incidence of AAA is 2-4% in the adult population.[6] AAA is 4-6 times more common in male siblings of known patients, with a risk of 20-30%.[71] Rupture of the AAA occurs in 1-3% of men aged 65 or more, the mortality is 70-95%.[3]

With the recent advancements in AAA research, AAA is ranked as the 13th leading cause of death in the US and the 10th leading cause of death in men over the age of 55 years.

Post-mortem studies have suggested that ninety-five percent of deaths from ruptured AAA occur at or above age 65; Eur J Vasc Endovasc Surg 21, 535–540 (2001) doi:10.1053/ejvs.2001.1368
cgs file: scott-AAA.pdf

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