Now, in addition to all the other stuff there, you can go to Kmart and get screened for abdominal aortic aneurysm (AAA). Some people will even receive free ultrasound tests. The new program, from the Find the AAAnswers Coalition, was announced on Friday. It’s a perfect example of disease mongering, the selling of a sickness to increase sales of a drug or device.
In this case, the expenses of the program and the coalition are entirely underwritten by Medtronic, which sells abdominal stent grafts used to repair AAAs, and the members of the coalition include organizations like the Peripheral Vascular Surgical Society, the Society for Vascular Surgery, and the Society for Vascular Ultrasound, whose members may derive a significant portion of their income from performing AAA repairs and screening.
No one is disputing that AAA is a bad thing, or that, when appropriate, AAA repair is a life-saving procedure. As noted correctly on the Find the AAAnswers Coalition website, a ruptured AAA is a catastrophic event. Most people with a ruptured AAA outside the hospital don’t survive, making AAA the third leading cause of sudden death in men over 60.
But that doesn’t mean that more widespread screening is in the best interest of the public. Here’s the problem: the US Preventive Services Task Force (USPSTF) guidelines for AAA screening are the best current source for information about who is eligible for AAA screening. The USPSTF guidelines recommend against routine screening for women, for instance, while the Kmart-Medtronic program is much more liberal, recommending that a 65 year old woman with no other risk factors except a history of smoking undergo ultrasound. (Everyone agrees that a repair procedure is indicated when ultrasound finds a AAA larger than 5.5 cm.)
Now you might well wonder about the harms associated with screening, especially with a test such as ultrasound, which is entirely noninvasive, and especially when a big company like Medtronic is picking up the tab. In fact, a vascular surgeon who spoke to me on behalf of the coalition told me that ultrasound screening for AAA carries
no risk: ultrasound will not identify people who will end up being treated who should not be treated. If you have an aneurysm as diagnosed on ultrasound you will benefit if it’s greater than 5 cm or greater. The data are very clear: there is no overtreatment– once an aneurysm has been identified there is no risk of overtreating or mistreating it.
But the surgeon is wrong. Any screening program and any treatment procedure has both risks and benefits. The surgeons may not like to think about it, but even a life-saving procedure like AAA repair can be harmful if performed in the wrong population. This is why we need an objective and impartial gatekeeper, like the USPSTF. And the USPSTF guidelines are quite clear about this, repeatedly asserting that there are significant dangers associated with inappropriate AAA screening. Here, for example, is what the USPSTF has to say about screening women:
Because of the low prevalence of large AAAs in women, the number of AAA-related deaths that can be prevented by screening this population is small. There is good evidence that screening and early treatment result in important harms, including an increased number of surgeries with associated morbidity and mortality, and psychological harms. The USPSTF concluded that the harms of screening women for AAA outweigh the benefits.
So it turns out that the harms of over-screening are also significant and worthy of concern. I asked Joseph Ross, a researcher at Yale, to help me understand the implications of the Kmart-Medtronic screening program. Ross walked me through the math and painstakingly demonstrated how a seemingly beneficial screening procedure can actually cause harm. (Note that the numbers he uses are meant to illustrate the general concept and are not intended to represent a precise assessment of AAA screening.)
Here is a way to think about it epidemiologically. If screening has a sensitivity of 95% and a specificity of 99% for AAAs that are greater than 5 cm in diameter, then if there are 1000 high risk individuals undergoing screening (by high risk, I am assuming the population risk for a AAA > 5cm is 10%), then
- 95 of 100 with AAAs are CORRECTLY identified as having a AAA
- 5 of 100 with AAA are INCORRECTLY identified as not having a AAA
- 9 of 900 without AAAs are INCORRECTLY identified as having a AAA
- 891 of 900 without AAAs are CORRECTLY identified as not having a AAA
So, 104 people undergo repair (of whom 9 didn’t need it), which has pretty substantial risks.
However, now let’s look what happens with a lower risk population — I am now assuming the population risk for a AAA > 5cm is 1% among 100,000 lower risk individuals undergoing screening, then
- 950 of 1000 with AAAs are CORRECTLY identified as having a AAA
- 50 of 1000 with AAA are INCORRECTLY identified as not having a AAA
- 990 of 99,000 without AAAs are INCORRECTLY identified as having a AAA
- 98,010 of 99,000 without AAAs are CORRECTLY identified as not having a AAA
Clearly, this gets ugly fast. Now 1940 people undergo repair (of whom 990 didn’t need it). That’s a lot of extra stents/surgeries – because when they go in for repair and find a 3.5 cm, rather than a 5 cm, surgeons are unlikely just to close it up. They put in a stent to “stabilize it” and reduce the likelihood of needing full repair – without any evidence.
The only possible defense for expanded screening is that newer or better data than that available to the USPSTF demonstrate that the benefits of expanded screening in fact outweigh the disadvantages. But the Kmart-Medtronic risk calculator doesn’t provide any explanation for its risk calculations, and it never specifically justifies or explains why it deviates from the USPSTF guidelines.
In other words, Medtronic and the coalition members, entirely on their own, set up their own screening program from which they will all benefit financially. The program has no oversight or peer review and never explains its process or methodology. By contrast, the USPSTF guidelines are created by an independent panel of experts who review the scientific evidence and publish their findings in well-documented publications, with all the evidence on full display for anyone to review.
Not all blue light specials turn out to be a good bargain.