The MD Daily Contract review

August 16, 2018 • By Guest

Should we continue to screen for abdominal aortic aneurysm?


Since 2005, the United States Prevention Task Force (USPTF) has recommended, with a “B” rating, screening for Abdominal Aortic Aneurysm (AAA) via abdominal ultrasound in men older than 65 years of age who have any history of tobacco smoking. Similar recommendations are in place in Sweden and the UK. These widespread recommendations are based on four randomized trials that began to look at the benefits of screening back in the 1980s and 1990s. Since then, mortality related to AAA rupture has decreased, yet it is not clear that these benefits should be attributed to screening protocols.

What are the real benefits of AAA screening?

These four landmark studies evaluating AAA are the Multicentre Aneursym Screening Study (MASS), the Chichester United Kingdom study (the only to include women), the Viborg County Denmark study and the western Australia study.1,2,3,4 All except the western Australian cohort identified a reduction in AAA rupture and emergency surgeries at 13 to 15 years follow up for those individuals who were screened.5 A more recent study looking at men in Sweden, showed that over a six year follow up, there was a 24% non-significant reduction in AAA mortality, which corresponds to two men avoiding death for every 10,000 men screened.6 Of course, this more recent study has a much shorter follow up than the landmark studies. This is significant as it is likely that a 10 year follow up is necessary to adequately evaluate the benefits of AAA screening6 as AAA related death in the 5 to 12 years following screening is rare in patients with an initially normal aorta.5

What are the concerns associated with AAA screening?

Despite the benefits in regard to rupture and emergent surgery, screening did not show an overall mortality benefit over 15 years (4 studies), but rather showed an increase in AAA over diagnosis and increased elective surgeries.5 In the Swedish study, 49 and 19 men out of 10,000 men were over-diagnosed and had elective surgery respectively.6 While there was an overall trend in in decreased death from AAA over the decades, this was also found in Swedish counties that did not provide AAA screen, suggesting that other factors, such as smoking reduction, were responsible for the improved mortality.6 Furthermore, the majority of research has focused on white males, decreasing the generalizability to other demographic groups. Based on the single study that included female subjects, the benefits of screening do not extend to women and the benefits to other racial groups remain is unclear.7 Finally all of these studies determined mortality based national registries, severely limiting the ability differentiate cause of death.

How can physicians continue to improve patient’s outcomes?

The seminal articles regarding AAA screening evaluate patients solely on age and smoking status, ignoring other significant and well known risk factors such as family history, cardiovascular disease, race, and body mass index. New research has taken this oversight into account and include an internally validated tool that could improve AAA screening based on such information.8 While this tool has yet to be externally validated, it is a good step in ensuring that screening targets groups who will most benefit from it. Importantly, healthcare providers must continue to encourage patients to minimize modifiable risk factors, most noticeably smoking.

The data regarding AAA screening is outdated, based on individuals initially screened back in the 1980s and 1990s. The studies are limited because they ignore important risk factors such as family history and cardiovascular disease, which are significant in terms of risk of death. Furthermore, the studies looked primarily at white males, decreasing their generalizability to women and other racial groups. In light of the risk of overdiagnosis and overtreatment, it is important that the medical community pushes for updated information on which to base our AAA screening recommendations.

References

1. Ashton HA, Buxton MJ, Day NE, et al. The Multicentre Aneurysm Screening Study (Mass) into the Effect of Abdominal Aortic Aneurysm Screening on Mortality in Men: A Randomised Controlled Trial. Lancet. 2002;360(9345):1531-1539.

2. Lindholt JS, Juul S, Fasting H, Henneberg EW. Hospital Costs and Benefits of Screening for Abdominal Aortic Aneurysms. Results from a Randomised Population Screening Trial. Eur J Vasc Endovasc Surg. 2002;23(1):55-60. doi:10.1053/ejvs.2001.1534

3. Norman PE, Jamrozik K, Lawrence-Brown MM, et al. Population Based Randomised Controlled Trial on Impact of Screening on Mortality from Abdominal Aortic Aneurysm. BMJ. 2004;329(7477):1259. doi:10.1136/bmj.38272.478438.55

4. Scott RA, Wilson NM, Ashton HA, Kay DN. Influence of Screening on the Incidence of Ruptured Abdominal Aortic Aneurysm: 5-Year Results of a Randomized Controlled Study. Br J Surg. 1995;82(8):1066-1070.

5. Guirguis-Blake JM, Beil TL, Senger CA, Whitlock EP. Ultrasonography Screening for Abdominal Aortic Aneurysms: A Systematic Evidence Review for the U.S. Preventive Services Task Force. Ann Intern Med. 2014;160(5):321-329. doi:10.7326/M13-1844

6. Johansson M, Zahl PH, Siersma V, Jorgensen KJ, Marklund B, Brodersen J. Benefits and Harms of Screening Men for Abdominal Aortic Aneurysm in Sweden: A Registry-Based Cohort Study. Lancet. 2018;391(10138):2441-2447. doi:10.1016/S0140-6736(18)31031-6

7. Scott RA, Bridgewater SG, Ashton HA. Randomized Clinical Trial of Screening for Abdominal Aortic Aneurysm in Women. Br J Surg. 2002;89(3):283-285. doi:10.1046/j.0007-1323.2001.02014.x

8. Kent KC, Zwolak RM, Egorova NN, et al. Analysis of Risk Factors for Abdominal Aortic Aneurysm in a Cohort of More Than 3 Million Individuals. J Vasc Surg. 2010;52(3):539-548. doi:10.1016/j.jvs.2010.05.090

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