June 24, 2014 -- Adhering mostly to its draft statement
published in January, the U.S. Preventive Services Task Force (USPSTF) included
no big surprises in its new recommendations in favor of ultrasound screening for
abdominal aortic aneurysms (AAAs).
In a notable change from its previous 2005
statement, the task force added nuance to its recommendations for ultrasound
screening for AAA in women, providing separate guidance for women who have
smoked and those who haven't. In 2005, USPSTF recommended against screening in
all women; however, the task force has now concluded that current evidence is
insufficient to assess the balance of benefits and harms of ultrasound
screening in women 65 to 75 who have ever smoked. It continues to recommend
against screening in women who have never smoked.
The final recommendations, which were
published online June 23 in the Annals of Internal Medicine,
also retained the task force's 2005 B-grade recommendation for one-time ultrasound
screening for AAA in men 65 to 75 who have ever smoked. In keeping with a
change to the definition of its C grade level, USPSTF now suggests selective
screening for men of this age group who have never smoked. In 2005, the same C
grade level indicated that the task force made no recommendation for or against
screening.
AAA screening in women
The task force noted that only one
randomized, controlled trial on AAA screening included women, and the trial
found no difference in AAA rupture, AAA-specific mortality, or all-cause
mortality between screened women and a control group. The group also pointed
out that women age 70 years who have ever smoked have an overall AAA rupture
prevalence of approximately 0.8%, while current smokers have a prevalence of approximately
2%.
"However, the single [randomized,
controlled trial] of screening for AAA that included women was underpowered to
draw definitive conclusions by sex, and the prevalence of AAA in women who
currently smoke approaches that of men who have never smoked," they wrote.
"As such, a small net benefit might exist for this population and
appropriate, high-quality research designs should be used to address this
question."
As a result, the task force determined that
the evidence was inadequate to conclude whether one-time ultrasound screening
for AAA was beneficial in women ages 65 to 75 years who have ever smoked.
The task force also said that the prevalence
of AAA in women who have never smoked ranges from only 0.03% to 0.6% for ages
50 to 79, and there is no evidence of apparent benefit of screening for AAA in
this group of women.
"The USPSTF therefore concludes that
adequate evidence shows that the absolute benefit of one-time screening for AAA
with ultrasonography in women who have never smoked can effectively be bounded
at none or almost none," the group wrote.
The task force also observed that women had
a slightly higher risk of AAA surgery-related death than men. Women had 7%
operative mortality with open repair, compared with 5% for men, and 2% for
endovascular repair, compared with 1% for men.
"Convincing evidence shows that the
harms associated with one-time screening for AAA with ultrasonography are at
least small in all populations and potentially higher in women because of their
higher risk for operative mortality," they wrote.
AAA screening in men
The task force reiterated that there is
convincing evidence that one-time ultrasound screening for AAA yields a
moderate benefit in men ages 65 to 75 years who have ever smoked. However, the
lower prevalence of AAA in men who have never smoked substantially reduces the
absolute benefit of screening in this group of men.
"Despite the demonstrated benefits of
screening for AAA in men overall, the lower prevalence of AAA in male
never-smokers versus male ever-smokers suggests that clinicians should consider
a patient's risk factors and the potential for harm before screening for AAA
rather than routinely offering screening to all male never-smokers," the
task force wrote.
The group noted that important risk factors
for AAA include older age and a first-degree relative with an AAA; other risk
factors include a history of other vascular aneurysms, coronary artery disease,
cerebrovascular disease, atherosclerosis, hypercholesterolemia, obesity, and
hypertension. Also, factors associated with a reduced risk for AAA include
African-American race, Hispanic ethnicity, and diabetes.
Draft changes
Changes made to the draft version included
clarification of the definition of an "ever-smoker" and information
about the absolute benefits of screening for AAA to provide additional context
for the reported reductions in relative risk, according to the task force.
USPSTF also expanded the discussion relating to the risks and benefits of
screening and treatment in women compared with those in men.
"Finally, the USPSTF emphasized that
more research -- including high-quality modeling studies -- is required to
better understand the relative benefits and harms of screening for AAA in men
and women with a family history of AAA and for women who have ever
smoked," they wrote.
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