AIM: CCTA Screening not ready for prime time
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| Calcified and noncalcified plaque by CCTA. Source: Fabian Bamberg, MD, University of Munich |
“Screening CCTA should not be considered a justifiable test at this time,” wrote John W. McEvoy, MB, of Johns Hopkins Ciccarone Center for the Prevention of Heart Disease in Baltimore, and colleagues. Also, an accompanying Archives editorial cautioned of the dangers of an epidemic of coronary pseudodisease and called for large-scale trials to better determine the risks and benefits of screening CCTA.
With more than half of coronary heart disease (CHD) deaths occurring in previously asymptomatic patients, interest in early detection is high. CCTA offers high sensitivity for detection of atherosclerosis and has been suggested for assessing symptomatic and asymptomatic patients.
McEvoy and colleagues sought to examine the downstream impact of CCTA screening and designed a matched cohort study of 1,000 individuals who participated in a screening study at Seoul National Bundang Hospital in South Korea, and an equal number of asymptomatic individuals who did not opt in for CCTA as part of the health screening program. The mean age among the total study population was 50 years and 63 percent were male.
The researchers prospectively followed the study population for 18 months and recorded data about medication use, secondary tests (exercise ECG stress testing, SPECT, coronary angiography, percutaneous intervention [PCI] or coronary artery bypass grafting [CABG]) and cardiac events.
Among the 1,000 patients who underwent CCTA screening, 79 percent had a normal result. Among the 215 patients with CCTA positive results, atherosclerotic plaque was seen in 392 segments (2 +/- 1 segments per subject), 5 percent had significant (>50 percent) stenosis and 2 percent had severe (>75 percent) stenosis, reported McEvoy et al.
The researchers noted an association between positive CCTA results and statin prescriptions and aspirin use at the index visit. Statins were prescribed more often in subjects with positive CCTA results compared with the control group. At 90 days, 34.4 percent of patients with positive CCTA used statins compared with 8 percent in the control group. At 18 months, the figures dropped to 20 percent and 6 percent, respectively.
Similarly, physicians were more likely to prescribe aspirin to patients with positive CCTA results at the 90-day index visit, with 39.5 percent of patients receiving a prescription, up from 13 percent who used aspirin therapy at baseline. At the 18-month follow-up visit, 26.5 percent of all CCTA positive patients had continued with aspirin therapy.
The authors also noted reduced aspirin and statin use among patients with a normal CCTA result and suggested that the finding could be interpreted as either cost-effective or potentially harmful.
Although referrals for secondary testing were more common in the CCTA group, patients with positive results were more likely to undergo downstream testing, with 21 percent of this subgroup being referred for downstream testing compared to 1.4 percent of patients with normal CCTA results.
Furthermore, at 90 days, 12 CCTA patients had PCI and one had CABG compared with one case of PCI in the control group. “After 18 months, there was one admission for unstable angina in the CCTA group and one unspecified cardiac death in the control group.”
McEvoy and colleagues suggested that their “findings argue for randomized trials in this area,” adding, “These 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.”
The researchers emphasized that their results do not apply to patients with angina symptoms or coronary artery calcification testing of asymptomatic patients.
In accompanying invited Archives commentary, Michael S. Lauer, MD, of the division of cardiovascular sciences at National Heart, Lung and Blood Institute in Bethesda, Md., cautioned of an epidemic of pseudodisease, warning that screening for atherosclerosis may lead to more diagnoses and more interventions without preventing advanced disease or death.
“Overdiagnosis,” wrote Lauer, “is a serious problem because it leads to a number of harms, while by its very nature cannot offer benefit.” Physicians cannot ignore screening findings because the information does not tell them whether disease will remain subclinical, progress to advanced disease or progress slowly with the patient dying with the disease, not from the disease.
At the same time, additional tests to refine the diagnosis and treatments designed to prevent advanced disease are associated with risk and may harm the patient.
“The report of McEvoy et al serves as a reminder of the two-edged effects of screening,” wrote Lauer, who called on physicians “to muster the courage, imagination and discipline to design and perform the needed large-scale trials” to prevent an epidemic of pseudodisease.