Analysis Too Much Medicine

Estimating overdiagnosis in screening for abdominal aortic aneurysm: could a change in smoking habits and lowered aortic diameter tip the balance of screening towards harm?

BMJ 2015; 350 doi: https://doi.org/10.1136/bmj.h825 (Published 04 March 2015) Cite this as: BMJ 2015;350:h825
  1. Minna Johansson, PhD student1,
  2. Anders Hansson, researcher1,
  3. John Brodersen, associate professor2
  1. 1Department of Public Health and Community Medicine, Institute of Medicine, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. Research Unit and Section for General Practice, FoUU-centrum Fyrbodal, Vänersborg, Sweden
  2. 2Research Unit for General Practice and Section of General Practice, Department of Public Health, University of Copenhagen, Copenhagen, Denmark
  1. Correspondence to: M Johansson minna.johansson{at}vgregion.se
  • Accepted 2 December 2014

Summary box

  • Clinical context—Abdominal aortic aneurysms (AAAs) are often asymptomatic until they rupture, when the death rate is greater than 80%. If diagnosed before rupture, AAA can be treated with surgery, which has a mortality of 4-5%

  • Diagnostic change Sweden, the UK, and the US have initiated screening programmes for AAA. There are also proposals to change the aortic diameter for diagnosis from ≥30 mm to 25 mm

  • Rationale for change—Early diagnosis by screening allows the opportunity of surgery to prevent ruptures

  • Leap of faith—Detecting asymptomatic aneurysms will reduce AAA mortality and morbidity

  • Impact on prevalenceOur estimates indicate that screening almost doubles AAA prevalence, but most AAAs are small and at low risk of rupture. Changing the definition of an AAA from 30 mm to 25 mm would double prevalence again

  • Evidence of overdiagnosis—We estimate that if 10 000 men are invited to screening, 46 AAA deaths can be prevented over 13-15 years but 176 would have an AAA ≥30 mm detected that remained asymptomatic after 13 years. A recent drop in AAA prevalence reduces the benefits of screening and worsens the benefit:harm ratio

  • Harms of overdiagnosisAsymptomatic men are labelled at risk of a life threatening condition for which they will be under lifelong surveillance. Of 10 000 men invited to AAA screening, 37 (95% confidence interval 15 to 60) overdiagnosed men had unnecessary preventive surgery, of whom 1.6 (1.4 to 1.7) died

  • Limitations—Figures for exact calculations of overdiagnosis are not available and unlikely to emerge. The psychosocial consequences of living with a screen detected AAA are inadequately investigated. Cost effectiveness data on screening are inconclusive

  • Conclusion Screening programmes have changed the meaning of an AAA diagnosis from a life threatening condition to a risk factor. AAA screening programmes should be …

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