What Is the Impact of Screening Low Risk Patients with CT Angiography?

In a study published online in Archives of Internal Medicine, John McEvoy and colleagues examine the impact of screening low risk patients with coronary CT angiography (CTA). They compared 1000 South Korean patients who underwent CTA and compared them to 1000 matched controls.

CTA identified 215 people with coronary atherosclerosis. At 90 days and at 18 months, statins and aspirin were being taken by a significantly higher percentage of patients in the CTA+ group than in the CTA- group or in the matched control group:

At 90 days

  • statins were used in 34% of CTA+ patients vs 5% of CTA- patients vs 8% of controls
  • aspirin was used in 40% vs 5% vs 8%

At 18 months

  • statins were used in 20% vs 3% vs 6%
  • aspirin was used in 26% vs 3% vs 6%

The investigators also found that at 90 days there were more secondary tests and revascularizations in the CTA group than in controls:

  • secondary tests: 5% vs 2%, p < .001
  • revascularizations: 1% vs 0.1%, p < .001

At 18 months there was one cardiovascular event in each group.

The authors observed that in their study “we found that the evidence-free performance of CCTA in asymptomatic patients was associated with further evidence-free testing and interventions.” They concluded that their data “concurs with the prevailing notion that screening CCTA does not have a role in low-risk patients.”

In an invited commentary, Michael Lauer said the study “serves as a powerful reminder of the 2-edged effects of screening.” He continues:

The only way to know whether screening by CCTA leads to clinically beneficial diagnosis of real disease, as opposed to pseudodisease, is by performing large-scale controlled trials, preferably with randomization. We cannot simply assume that just because a screening test predicts clinical outcomes, interventions necessarily will prevent them. Similarly, we cannot assume that because other tests diagnose disease that responds to treatment, a new screening test must do the same.

Here is the press release from JAMA/Archives:

Low-Risk Patients Screened for Heart Disease Tend to Receive More Preventive Care and Testing, but Their Outcomes May Not Be Any Different

CHICAGO – Screening for coronary heart disease (CHD) among individuals at low risk of the condition is associated with increased use of medications (such as aspirin and statins) and increased additional testing, but no difference in cardiac events at 18 months, according to a report posted online today that will be published in the August 8 print issue of Archives of Internal Medicine, one of the JAMA/Archives journals. The article is part of the journal’s Less Is More series.

Coronary heart disease is associated with atherosclerosis, a process in which plaque builds up in the lining of the arteries. More than half of deaths attributed to CHD occur in people who have no signs of heart trouble, according to background information in the article. Coronary computed tomographic angiography (CCTA), a test that uses X-rays to provide a clear look at the heart and arteries, has been suggested as a tool for screening low-risk patients for CHD. “Given the potential for more widespread use of CCTA in cardiac risk evaluation, we sought to evaluate the downstream implications of CCTA testing,” write the authors.

John W. McEvoy, M.B., B.Ch., B.A.O., M.R.C.P.I., from Johns Hopkins Ciccarone Center for the Prevention of Heart Disease, Baltimore, and colleagues studied the effect of CCTA in patients who were not at high risk for CHD. From a health screening program conducted at Seoul National University Bundang Hospital in Seoul, South Korea, they selected 1,000 patients who had chosen to undergo CCTA testing and 1,000 patients who did not; neither group had CHD symptoms. At three months and 18 months later, the researchers examined medication use, secondary test referrals, surgical restoration of the blood supply (revascularization) and cardiovascular incidents.

Among the group that had been screened, 215 patients (21 percent) tested positive for signs of atherosclerosis. Those patients were more likely to receive prescriptions for medication at the initial visit and subsequently more likely to undergo further testing and take aspirin and cholesterol-lowering statin drugs during the follow-up period. Patients who had been screened by CCTA were more likely to undergo revascularization, but not to experience cardiovascular events; by 18 months, one such incident had occurred in both the screened and the unscreened groups.

The authors concluded that “physicians and patients may dramatically change practice based on CCTA findings,” and call for further study of the implications of this shift, especially in patients at higher risk of CHD. They also point out that the increase in preventive interventions in patients with positive CCTA results did not appear to significantly reduce the risk of cardiovascular incidents, when compared with patients who did not undergo CCTA testing. “Thus,” they conclude, “the potential benefit of increased medication use in the CCTA group is tempered by the risk of further testing in low-risk patients without any evidence-based indication.”

(Arch Intern Med. 2011;10.1001/archinternmed.2011.204.)

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