Asymptomatic, low-risk patients with abnormal results on screening coronary computed tomographic angiography tend to undergo further invasive procedures and to initiate medical therapy, but don’t show better outcomes at 18 months than do those who aren’t screened, according to a report published online May 23 in Archives of Internal Medicine.
In addition, patients who receive normal results on CCTA screening tend to discontinue aspirin or statin use. "Whether this will prove to be cost effective or potentially harmful owing to a false sense of reassurance is currently unknown," according to Dr. John W. McEvoy of Johns Hopkins Ciccarone Center for the Prevention of Heart Disease, Baltimore, and his associates.
Both findings demonstrate that physicians and patients sometimes "dramatically change practice based on CCTA findings," so rigorous randomized controlled trials that closely examine the usefulness of this imaging technique are called for, they added.
The investigators "sought to evaluate the downstream implications of CCTA testing" in what they described as the first study to examine the issue in a large matched cohort. They used data from a group of 1,000 asymptomatic, low-risk South Korean adults who had already undergone CCTA as part of a 6-month health-promotion effort at Seoul National University Bundang Hospital, as well as 1,000 matched subjects who declined to have CCTA in that promotion.
The mean age of the study population was 50 years, and 63% of the subjects were men.
The majority, 79%, had normal CCTA results; 21% had abnormal results. This included 7% who were found to have significant coronary artery stenosis.
Significantly more (5.5%) of the subjects who underwent CCTA were referred for further testing, including myocardial single-photon emission CT (SPECT) and coronary angiography, compared with subjects who did not have CCTA (2.2%). Yet the percentage of abnormal SPECT results was the same in both groups.
Revascularization procedures also were more common in the CCTA group (13 subjects) than in the control group (1 subject), "despite their asymptomatic status and low Framingham Risk Score." Twelve patients underwent PCI and 1 underwent CABG in the CCTA group.
However, the rate of major coronary events was extremely low (0.1%) and identical between the two study groups, regardless of CCTA screening status.
"This raises great concern regarding the use of CCTA imaging in low-risk groups," Dr. McEvoy and his associates said (Arch. Intern. Med. 2011 May 23 [doi:10.1001/archinternmed.2011.204]).
"Our data concur with the prevailing notion that screening CCTA does not have a role in low-risk patients."
Subjects who underwent CCTA had increased rates of statin use compared with those who did not, both at 90 days (34% vs. 8%) and 18 months (20% vs. 6%). The odds ratio for statin use among subjects who had abnormal CCTA results was 4.6, compared with subjects who did not undergo CCTA.
Abnormal CCTA results also were associated with an increased use of aspirin. The odds ratio for aspirin use among subjects who had abnormal CCTA findings was 6.8 at 90 days and 4.2 at 18 months, compared with subjects who did not undergo CCTA.
It was interesting to note that the use of both medications decreased markedly over time in both groups. This "serves as a reminder that medication compliance is a complex phenomenon determined only in part by a single health care intervention (such as an imaging test like CCTA)," the investigators noted.
Overall, the study findings "highlight the need to consider the pretest probability of disease before performing imaging tests in patients who may be subsequently exposed to potentially harmful downstream procedures with questionable prognostic benefit," they said.
In an accompanying editorial, Dr. Michael S. Lauer wrote: "The report by McEvoy et al. serves as a powerful reminder of the two-edged effects of screening."
"Overdiagnosis is threatening to become an increasingly important public health problem because of the enthusiasm for and proliferation of unproven screening tests," he said (Arch. Intern. Med. 2011 May 23 [doi:10.1001/archinternmed.2011.205]).
"If we are going to prevent an epidemic of coronary pseudodisease, we as a profession will have to muster the courage, imagination, and discipline to design and perform the needed large-scale trials" to determine whether CCTA actually improves patient outcomes, said Dr. Lauer of the National Heart, Lung, and Blood Institute.
Dr. McEvoy and Dr. Lauer reported no relevant financial disclosures.