NEW YORK (GenomeWeb) – Results of a single-center retrospective study focusing on a predominately African-American patient population have added to mounting evidence that Corus CAD, CardioDx's gene expression-based coronary artery disease rule-out test, can help clinicians avoid unnecessary referrals to cardiology or advanced cardiac testing.
Researchers from CardioDx and Providence Medical Group in Dayton, Ohio presented the study results this week in a poster at the Annual North American Meeting of the Society for Medical Decision Making in Miami.
In the study, which was initiated by the Dayton group and funded by CardioDx, the team tracked 518 African-American patients who presented with symptoms suggestive of obstructive coronary artery disease between 2011 and 2013, and assessed the impact of Corus CAD results on physician decision-making.
Corus CAD — which CardioDx performs in its CLIA-certified laboratory in Redwood City, California — gauges the expression level of 23 genes in peripheral blood linked to the amount of plaque on the walls of coronary arteries. The algorithm underlying the test combines expression of these genes with patients' age and sex to yield a score between 1 and 40 that is associated with their risk of obstructive CAD with a 96 percent negative predictive value.
According to the researchers, patients in the Providence Medical Group study with Corus CAD scores less than or equal to 15 had a 95 percent lower rate of referral for advanced cardiac testing compared to patients with scores above 15. Only eight of 214 patients with a low score were referred for advanced testing, while 227 of 304 patients with a high score were sent on to additional follow-up.
"These results show that Corus CAD can be a powerful decision-making tool for clinicians guiding their African-American patients through the diagnostic pathway for suspected obstructive CAD," the study's lead author Morris Brown, of Providence Medical Group, said in a statement.
"Given the heterogeneity in clinical manifestations of suspected obstructive CAD amongst different ethnic populations in the US, a convenient and accurate blood test like Corus CAD that is effective across a spectrum of patients provides tremendous clinical value, particularly when it allows us to avoid costly and potentially harmful cardiac tests for patients who don't need them," he added.
The study did not compare patients who received Corus CAD to those who did not, to evaluate how the test changed physician decision-making relative to standard clinical assessment. It only looked at referral rates for patients with high versus low test scores.
CardioDx has conduced larger validation and utility studies: two prospective, multicenter US validation trials, PREDICT and COMPASS; and several utility studies, IMPACT-PCP, IMPACT-Cardiology, and REGISTRY I. The company has also sought to enrich the evidence for its test's clinical utility through smaller research efforts focused on specific patient populations.
For example, the firm also conducted a study with researchers from Vanderbilt University of 57 women enrolled in the larger IMPACT trial, which found that after cardiologists learned their patients' Corus CAD scores they changed their treatment plan for 60 percent, or 34 of the women.
In the Providence Medical Group's study, 41 percent of the cohort, a total of 214 patients, received a low CAD score. According to the researchers this especially supports the utility of a test like Corus CAD in the primary care setting, where costly follow up can potentially be avoided for a large percentage of patients.
According to the authors, the study provides important direct evidence that the test's utility in the African-American population matches its performance in prior utility studies, which had largely non-minority subjects.
CardioDx Chief Medical Officer Mark Monane also said in a statement that the results are "consistent with the positive feedback we've been receiving from the primary care clinicians using the test in everyday clinical practice."
According to the company, over 75,000 Corus CAD test results have now been commercially delivered to clinicians. An estimated 49 million US Medicare beneficiaries have access to the Corus CAD test as a covered benefit. Another 22 million are covered for the test under Aetna and Coventry Health.