New data supports clinical utility and validity of Corus CAD blood-based gene expression test

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CardioDx has announced new data from three studies supporting the clinical validity and utility of Corus CAD, the company’s blood-based gene expression test to safely, accurately and conveniently help clinicians determine whether or not patient symptoms are due to obstructive coronary arterial disease (CAD). Data was presented at the American Heart Association Scientific Sessions 2012. 

Corus CAD is a decision-making tool that can help primary care clinicians and cardiologists exclude obstructive coronary arterial disease as the cause of a stable non-diabetic patient’s symptoms. The test involves a routine blood draw conveniently administered in the clinician’s office, and does not expose patients to risk of radiation or imaging agent intolerance. It is the only sex-specific test for obstructive CAD, accounting for critical biological differences between men and women. Corus CAD has now been used to assess more than 31,000 US patients.

Clinical validity


Two studies supporting the clinical validity of Corus CAD by Szilard Voros, associate professor of Medicine/Cardiology and Radiology at Stony Brook University, in collaboration with other investigators, analysed results from more than 600 patients in the PREDICT and COMPASS validation studies of Corus CAD. The first study examined expression of individual genes in the Corus CAD algorithm in relationship to maximum percent stenosis, coronary artery calcification, and coronary plaque composition, as measured by coronary CT angiography. This analysis showed that coronary calcium is associated with only a subset of the Corus CAD genes that reflect overall maximum per cent stenosis.


The second study showed that coronary artery plaque burden and maximum per cent stenosis significantly correlate with Corus CAD scores, as measured by cardiovascular CT angiography. In particular, these data showed that the Corus CAD score correlated with both calcified and non-calcified plaque, but was more significantly associated with non-calcified plaque.


“These two studies help illuminate our understanding of the Corus CAD gene expression test, and show that the Corus CAD scores are not only associated with the presence of obstructive coronary arterial disease, but may also provide insight into the amount of plaque, the kind of plaque, and the degree of narrowing of the coronary vessel,” said Voros.


Clinical utility


The clinical utility study, by lead author Kelly Parsons, senior Research manager at Express Scripts, showed that physicians’ use of Corus CAD was associated with increased medication adherence among patients prescribed lipid-lowering therapy. Results of the study showed that patients with elevated Corus CAD scores (>15), indicating greater plaque burden and increased likelihood of obstructive CAD, were more adherent to prescribed lipid-lowering agents (75% vs. 64%, p<0.05).


“Lipid-lowering medications, such as statins and fibrates, are critical for the management of cardiovascular disease,” said Mark Monane, chief medical officer of CardioDx. “Although US$20 billion is spent annually on lipid-lowering agents, long-term studies on this class show adherence rates to be only 40 to 60%. This study suggests that Corus CAD may be a useful tool for improving medication adherence among patients who have been prescribed lipid-lowering agents.”


The Corus CAD gene expression test has been validated in three independent patient cohorts enrolled as part of two prospective, multicentre studies, PREDICT and COMPASS. The PREDICT study first validated the ability of Corus CAD to assess whether or not a stable, non-diabetic patient’s symptoms are duetoobstructive CAD. In the COMPASS validation study, Corus CAD demonstrated very high negative predictive value (96%) in a patient population reflecting the test’s intended-use population, outperforming myocardial perfusion imaging (MPI) in diagnostic accuracy and negative predictive value. In these studies, Corus CAD was validated using CT angiography and the gold standard for diagnosis of coronary arterial disease, invasive coronary angiography. 

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