JNC: SPECT has prognostic value in diabetics, but is it cost effective?
Jacobijne J. Wiersma, MD, and colleagues from Amstelland Hospital in Amstelveen, the Netherlands, performed a sub-analysis of 319 patients from the MERIDIAN trial, which was stopped early due to slow recruitment.
In the MERIDIAN trial, patients with diabetes, mild angina and reversible defects on SPECT were randomized to either continued medical therapy or early invasive treatment and outcomes were compared. The premature termination of the trial resulted in inadequate statistical power to test the original study hypothesis.
In the subanalysis, Wiersma and colleagues related the severity of the myocardial perfusion defects to the occurrence of cardiac death and non-fatal MI.
During follow-up of an average of two years, 14 patients had a cardiac event: three in 171 patients without myocardial ischemia and 11 in 148 patients with myocardial ischemia (26 percent moderate ischemia, 20 percent severe).
The annual event rates rose from 0.8 percent (no ischemia) to 1.5 percent (moderate) to 5.8 percent (severe). The differences were significant. Those with severe ischemia had a three- to six-fold increased risk of cardiac events compared with those with no or moderate ischemia. Researchers also found that insulin use was an independent predictor of cardiac events.
“The major value [of this subanalysis] is the demonstration of the accuracy of SPECT imaging for risk stratification in a prospectively identified patient population,” wrote Todd D. Miller, MD, and Leslee J. Shaw, PhD, in an accompanying editorial.
Prospective studies are not as influenced by patient selection bias as are retrospective studies, Miller and Shaw wrote. However, a major limitation of prospective studies of diabetics such as MERIDIAN “has been the failure to identify a large enough high-risk subset of patients to justify the widespread use of SPECT for risk stratification purposes in asymptomatic or mildly symptomatic diabetic patients.”
They detail three criteria that a test being applied primarily for risk stratification purposes should meet:
- the identification of a fairly large number of high-risk patients in the population being tested;
- the use of a different treatment strategy in these high-risk patients, which they would not have otherwise received if not for the results of the test and
- an improvement in outcome in the high-risk subset because of the different treatment strategy.
Current guidelines already call for more aggressive medical therapy for diabetics without coronary artery disease on the basis of their diabetes status.
“The major goal of noninvasive testing in diabetic patients should be to identify those with high-risk anatomical CAD,” Miller and Shaw wrote. “Future studies of SPECT MPI should determine in whom this approach will be cost effective.”