Screening directive upped ultrasounds for AAA without improving outcomes
September 20, 2012
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Stanford, CA - Medicare coverage of screening for abdominal aortic aneurysms (AAA) serves only to increase the number of abdominal ultrasounds performed and has no discernible effect on clinical outcomes, according to a new analysis [1]. Since the implementation of the Screening Abdominal Aortic Aneurysms Very Efficiently (SAAAVE) Act in 2007, the use abdominal ultrasonography increased from 7.6% among SAAAVE-eligible men in 2004 to 9.6% in 2009 without any changes in the rates of AAA repair, AAA rupture, or all-cause mortality.
"Furthermore, although two-thirds of men aged 65 years were eligible for AAA screening because of a history of ever smoking, fewer than 10% of men in this age group received any abdominal ultrasonography after 2007," write lead investigator Dr Jacqueline Baras Shreibati (Stanford University School of Medicine, CA) and colleagues in the report, published online September 17, 2012 in the Archives of Internal Medicine. "Consequently, most men who qualified for SAAAVE Act AAA screening did not undergo it."
In an editorial accompanying the study [2], Drs Russell Harris, Stacey Sheridan, and Linda Kinsinger (University of North Carolina, Chapel Hill) argue that while some may view the findings as "another example of unjustifiably slow diffusion of effective medical care into actual clinical practice," they contend that maybe the diffusion of increased AAA screening is not desirable. They suggest that the population benefit of screening is lower than it was previously and that the less invasive endovascular aortic repair (EVAR) intervention is being performed on smaller aneurysms with little clinical benefit.
"Perhaps most important, our understanding of the harms of screening have evolved, teaching us to look more closely, and with the patient's perspective, at the potential harms of labeling, overdiagnosis, and nonfatal complications of the intervention that are important features of AAA screening," write the editorialists. "Given these considerations, our weighing of benefits and harms for AAA screening may have changed."
To heartwire, Shreibati said the editorial raises important issues about the value of AAA screening and called their concerns perfectly legitimate. She noted, however, that the point of their paper was not to question the value of abdominal ultrasonography for AAA, but rather to assess the impact of the SAAAVE Act. In addition, the current analysis was not designed to address the low uptake of screening, but she hypothesized that there might not be enough awareness on the part of physicians or patients about AAA screening and its potential benefits. In addition, there may be concern about the relatively small absolute reduction in clinical events resulting from AAA screening.
"At the population level, the numbers are quite small, so there might be some hesitancy on the part of the physician or the patient to see the value of screening," she said. "I would suspect, however, that a lot would have to do with awareness of it. I think we're all aware that [prostate-specific antigen] PSA screening has been used in the past for prostate cancer, and we're all aware of colonoscopy, but abdominal ultrasound is not at all on the radar."
The 2005 USPSTF recommendations
In 2005, the US Preventive Services Task Force (USPSTF) recommended a one-time ultrasound screening for AAA in men aged 65 to 75 years old who were former or current smokers (grade B recommendation). The recommendations do not extend to men of the same age who never smoked, given findings of lower AAA-associated mortality, nor do they extend to women. In the present study, the researchers used data from Medicare claims between 2004 and 2008 to identify 374 310 men aged 65 years old eligible for screening and three control groups not eligible for screening. The three control arms included 70-year-old men, 76-year-old men, and 65-year-old women.
In terms of trends, there was a significantly larger increase in the use of abdominal ultrasound among SAAAVE-eligible men. In contrast to the 2% increase between 2004 and 2008 in screening-eligible men, there was a 0.7% increase in 70-year-old men and 76-year-old men, respectively, and a 0.9% increase in 65-year-old women. In a multivariate-adjusted model, the use of abdominal ultrasound in 65-year-old males was 15% higher compared with 70-year-old males, 17% compared with 76-year-old males, and 11% compared with 65-year-old females.
The overall rate of hospitalizations for AAA rupture was <0 .01=".01" act="act" all-cause="all-cause" all="all" also="also" analysis="analysis" and="and" associated="associated" changes="changes" clinical="clinical" elective="elective" enrollees="enrollees" events="events" females.="females." for="for" groups="groups" hospitalization="hospitalization" in="in" limit="limit" low.="low." low="low" male="male" medicare="medicare" might="might" mortality.="mortality." new="new" not="not" number="number" of="of" one-year="one-year" or="or" p="p" power="power" rate="rate" repair="repair" repairs="repairs" researchers.="researchers." rupture="rupture" saaave="saaave" say="say" statistical="statistical" the="the" these="these" three="three" was="was" with="with" zero="zero">
Trends suggest declining mortality from AAA
To heartwire, Shreibati said the group was surprised, even before the initiation of the SAAAVE act, that just 7.6% of eligible patients underwent AAA screening. Ideally, if every 65-year-old male with a history of smoking in the Medicare population underwent screening, the number would be as high as 60% of all males 65 years of age. "Instead, we're seeing just one-fifth of that," she said. As for the modest increase after the SAAAVE Act, she said it might be too early to see the full effect of its implementation.
As for the lack of reduction in clinical events, Shreibati suspects that the one-year follow-up might be too short to observe a reduction, especially in all-cause mortality. Most data suggest that such benefits would not likely to be observed until two years after screening. "Our primary objective was just to evaluate before and after the SAAAVE act," she said. "It would have been nice to see some type of clinical effect, but that would certainly deserve an additional study with longer follow-up."
Trends suggest declining mortality from AAA
In their editorial, Harris, Sheridan, and Kinsinger point out that evidence suggests the burden of AAA is decreasing, with mortality from ruptured AAA falling by as much as 50% in the past 10 to 15 years. "This reduction closely parallels the reduction in smoking prevalence and myocardial infarction incidence, and it started before AAA screening began," they write. "This argues that the true incidence of AAA is decreasing, perhaps with little contribution from screening. Thus, the potential benefit from AAA screening is decreasing."
In addition to these concerns, the editorial is critical of the rapid diffusion of the EVAR procedure to patients who should not be treated, such as those with AAA aneurysms <5 .5=".5" aaas="aaas" an="an" aneurysms="aneurysms" are="are" but="but" by="by" clinical="clinical" cm="cm" complications="complications" current="current" diameter.="diameter." documented="documented" evar="evar" f="f" from="from" harm="harm" in="in" increased="increased" life="life" little="little" may="may" more="more" of="of" overall="overall" p="p" patient="patient" people="people" pose="pose" procedure.="procedure." randomized="randomized" research="research" risk="risk" s="s" screening="screening" smaller="smaller" strategy="strategy" suggests="suggests" than="than" the="the" then="then" these="these" threat="threat" to="to" treated="treated" treatment="treatment" trials="trials" unnecessarily="unnecessarily" was="was" with="with">
Overall, they believe the USPSTF has will face a difficult challenge when updating the 2005 recommendations, as the evidence shows a lower benefit to screening than previously believed, say Harris, Sheridan, and Kinsinger. The harms of treatment might not have declined and may have increased with increasing use of EVAR.
