Screening diabetics for coronary disease does not 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 15 April issue of Journal of the American Medical Association (JAMA), a theme issue on diabetes.

Dr Frans J Th Wackers, Yale University School of Medicine, New Haven, USA, presented the findings of the study at a JAMA media briefing at the National Press Club in Washington, DC.

Wackers and colleagues of the Detection of Ischemia in Asymptomatic Diabetics (DIAD) study group tested prospectively whether systematic screening for coronary artery disease 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 coronary artery disease, patients were randomly assigned to be screened (n=561) for coronary artery disease with the imaging method of adenosine-stress radionuclide myocardial perfusion imaging, or not be screened (n=562). The average follow-up was 4.8 years.

The overall cumulative five-year cardiac event rate was 2.9% and averaged .6% per year, lower than anticipated. The researchers found that when analysed according to randomisation, there were 15 events (seven nonfatal heart attacks; eight cardiac deaths; 2.7%) in the screening group vs. 17 events (10 nonfatal heart attacks; seven cardiac deaths; 3%) in the no-screening group. Of those in the screened group, 409 participants (78%) with normal results and 50 (10%) with small myocardial perfusion imaging defects had lower event rates than the 33 with moderate or large MPI defects; .4% per year vs. 2.4% per year.

Coronary angiography was performed within 120 days after screening in 4.4% of 561 participants, including in 15% of 33 with moderate or large defects. In comparison, only three (.5%) of 562 participants in the no-screening group underwent angiography within 120 days after randomisation. The overall rate of coronary revascularisation was low in both groups: 5.5% in the screened group and 7.8% 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 coronary artery disease 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 wrote. “… participants had a low cardiac event rate and the identification of participants with abnormal screening results did not serve to eliminate their risk over five 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.”