Gene Expression Test More Effective Than Myocardial Perfusion Imaging

A blood-based gene expression test was more effective for ruling out obstructive coronary artery disease in stable symptomatic patients than myocardial perfusion imaging (MPI), a common test that uses a radioactive agent to evaluate the blood flow and function of the heart.

Gene expression testing provides valuable tissue and cell-specific information about the molecular mechanisms involved in disease processes, enabling progression at a given point in time. Genetic tests measure genetic variations, mutations, traits, and predispositions whereas gene expression testing assesses a dynamic process, integrating both genetic predisposition and additional behavioral and environmental influences on current disease state.

The Comprehensive Maintenance Program to Achieve Sustained Success (COMPASS) study enrolled 537 stable patients with symptoms suggestive of coronary artery disease who had been referred to MPI at 19 US sites. A blood sample was obtained in all patients prior to MPI, and gene expression testing was then performed with study investigators blinded to gene expression-test results.

In the COMPASS study, the gene expression test was superior to MPI in diagnostic accuracy, sensitivity (89 percent vs. 27 percent, p<0.001), and negative predictive value (96 percent vs. 88 percent, p<0.001) and demonstrated excellent performance for ruling out obstructive coronary artery disease relative to both invasive angiography and CTA.

The CardioDx (Palo Alto, CA, USA) gene expression test used in the study, called Corus CAD, measures the RNA levels of 23 genes from a whole blood sample. Because these RNA levels are increased or decreased when obstructive coronary artery disease is present, the Corus CAD score indicates the likelihood that an individual patient does not have obstructive coronary artery disease.

"Chest pain symptoms account for two percent of all visits to the doctor's office each year," said Dr. Mark Monane, chief medical officer of CardioDx. "Corus CAD has now been validated in more than 1,100 patients in three separate studies. For physicians, methods to improve the diagnosis of symptoms suggestive of coronary artery disease represent a huge unmet need, and the Corus CAD test may help clinicians make better decisions. For patients, the test may lead to better diagnostic accuracy as well as avoidance of unnecessary procedures. For payers, we believe that Corus CAD can address a major expense category."

The study results were presented by Dr. Gregory S. Thomas, clinical professor of medicine and director of nuclear cardiology education at the UC Irvine School of Medicine (Irvine, CA, USA) at the American Heart Association Scientific Sessions 2011 conference from November 12-16, 2011, in Orlando, (FL, USA).

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