Screening patients with diabetes for CAD does not significantly reduce risk of cardiac events

Screening for coronary artery disease in patients with type 2 diabetes did not result in a significant reduction in the rate of heart attacks or cardiac death compared to patients who were not screened, according to a study in the April 15 issue of JAMA, a theme issue on diabetes.

Frans J. Th. Wackers, M.D., Ph.D., of the Yale University School of Medicine, New Haven, Conn., presented the findings of the study at a JAMA media briefing at the National Press Club in Washington, D.C.

Almost 200 million people worldwide have type 2 diabetes. “Coronary artery disease (CAD) is a major health concern and the leading cause of death in individuals with type 2 diabetes. CAD is often asymptomatic [having no symptoms] in these patients until the onset of myocardial infarction [heart attack] or sudden cardiac death,” the authors write. There has been substantial interest in the early detection of asymptomatic CAD by screening of patients with type 2 diabetes. However, the potential of routine screening to alter treatment and to prevent cardiac events in persons without clinically apparent CAD is largely unknown, according to background information in the article.

Dr. Wackers and colleagues of the Detection of Ischemia in Asymptomatic Diabetics (DIAD) study group tested prospectively whether systematic screening for CAD would identify higher-risk individuals and beneficially affect their risk of heart attack or cardiac death. In the trial, that included 1,123 participants with type 2 diabetes and no symptoms of CAD, patients were randomly assigned to be screened (n = 561) for CAD with the imaging method of adenosine-stress radionuclide myocardial perfusion imaging (MPI), or not be screened (n = 562). The average follow-up was 4.8 years.

The overall cumulative 5-year cardiac event rate was 2.9 percent and averaged 0.6 percent per year, lower than anticipated. The researchers found that when analyzed according to randomization, there were 15 events (7 nonfatal heart attacks; 8 cardiac deaths; 2.7 percent ) in the screening group vs. 17 events (10 nonfatal heart attacks; 7 cardiac deaths; 3.0 percent) in the no-screening group. Of those in the screened group, 409 participants (78 percent) with normal results and 50 (10 percent) with small MPI defects had lower event rates than the 33 with moderate or large MPI defects; 0.4 percent per year vs. 2.4 percent per year.

Coronary angiography was performed within 120 days after screening in 4.4 percent of 561 participants, including in 15 percent of 33 with moderate or large defects. In comparison, only 3 (0.5 percent) of 562 participants in the no-screening group underwent angiography within 120 days after randomization. The overall rate of coronary revascularization was low in both groups: 5.5 percent in the screened group and 7.8 percent in the unscreened group. During the course of the study there was a significant and equivalent increase in primary medical prevention with aspirin, statins and angiotension-converting enzyme (ACE) inhibitors in both groups.

“The strategy of routine screening for CAD in patients with type 2 diabetes is based on the premise that testing could accurately identify a significant number of individuals at particularly high risk and lead to various interventions that prevent cardiac events. However, the results of the DIAD study would appear to refute this notion,” the authors write. “… participants had a low cardiac event rate and the identification of participants with abnormal screening results did not serve to eliminate their risk over 5 years of follow-up.”

“However, rather than viewing this study as a negative screening study, clinicians might consider the results as a positive message: patients with type 2 diabetes without symptoms to suggest CAD, receiving contemporary medical care, close follow-up, and appropriate diagnostic evaluation for symptoms of ischemia have relatively favorable outcomes in the current era.”

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