Screening For AAA Comes Under Renewed Scrutiny And Criticism

A 2007 Medicare initiative to increase AAA (abdominal aortic aneurysm) screening in appropriate patients failed to prevent AAA rupture or reduce all-cause mortality, according to a new study published in Archives of Internal Medicine. The larger implications of the study are unclear, but two accompanying papers, an invited commentary and a perspective, emphasize the darker side of AAA screening.

Jacqueline Baras Shreibati and colleagues examined the effect of the 2007 Screening Abdominal Aortic Aneurysms Very Efficiently (SAAAVE) Act which provided Medicare coverage for a one-time ultrasound screening for new Medicare patients who were men and who had a history of smoking or women with a family history of AAA. The SAAAVE Act was based on 2005 US Preventive Services Task Force recommendations.

Using Medicare data from 2004 to 2008, the investigators found a modest increase in AAA screening among eligible 65-year-old Medicare men during the study period, from 7.6% in 2004 to 9.6% in 2008. The SAAAVE Act resulted in no significant differences in the rates of AAA repair, AAA rupture, or all-cause mortality, they concluded.

In an invited commentary, Russell Harris, Stacey Sheridan, and Linda Kinsinger write that the evidence about AAA screening has changed since the 2005 USPSTF recommendations. In the past 10-15 years, they write, mortality from ruptured AAA has been cut nearly in half. AAA screening, they maintain, has had little to do with this change; rather, the change is more likely due to long term trends in the reduction of smoking prevalence and the incidence of MI.

An additional trend over this period is the increased use of the endovascular aneurysm repair (EVAR) instead of open aneurysm repair (OAR) in patients with AAA. Although EVAR and OAR have similar long-term outcomes in randomized trials, in clinical practice EVAR is more likely to be performed in patients with AAAs smaller than the 5.5-cm threshold in which a beneficial effect has been demonstrated. The authors also point out that even if patients with small AAAs do not undergo an unnecessary procedure, they may suffer from the “negative psychological effects from diagnosis of small AAAs.”

One of the authors, David Harris, was a member of the 2005 USPSTF committee and voted in favor of the screening recommendation. A reconsideration of the guidelines may lead to a tightening of these recommendations, the authors suggest:

Sometimes it takes time to fully understand the effects of a new screening policy within the context in which it is introduced. If AAA mortality is declining without much contribution from AAA screening; if EVAR is a technology that is hard to control; if AAA screening leads to substantial harms by labeling and overdiagnosis, then perhaps it is a good thing that the USPSTF will get a chance to reevaluate its positive recommendation before more and more people develop the habit of screening. The outcome this time may be different.

In the accompanying perspective, Vinay Prasad presents the case history of a 65-year-old former smoker with a history of MI who had a 6 cm AAA. After consultation with his physician and his surgeon Mr. R underwent EVAR. After numerous complications causing significant reductions in his quality of life, Mr. R came to regret his decision. Prasad writes that the case raises several difficult issues:

First, Mr R was appropriately consented for surgery; however, in hindsight he wishes different information were presented to him. The informed consent process is often long and complicated, but it remains unclear if it best communicates what some patients want to know. Second, translating data from RCTs to individual patients, who often differ from those participants in the RCTs, remains an uncertain affair. Third, data are often extrapolated from older studies. The data from the cited screening example were collected between 1997 and 1999, prior to the development of endovascular repair. Finally, how quickly should physicians respond to new data, and are data from only 1 or 2 studies sufficient to change practice?

Further reading: Two years ago I wrote about a Medtronic-sponsored program providing free AAA screening at K-Mart: Blue light special: AAA screening at Kmart in the disease-mongering aisle. (Medtronic manufactures stent grafts used in EVAR procedures.)

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