Gene Expression Test May Shorten Coronary Disease Workup

Kate Johnson

October 11, 2013

DALLAS — A blood test that measures the expression of 23 genes to gauge the likelihood of obstructive coronary disease is less expensive than standard diagnostic testing, and reduces the rate of unnecessary invasive tests in women with symptoms of coronary artery disease (CAD).

The Corus CAD gene-expression test, developed by CardioDx, is "the only sex-specific test — accounting for biologic differences between genders — making it ideal as a first-line diagnostic modality, ahead of noninvasive imaging, to rule out CAD," said Joseph Ladapo, MD, from the NYU Langone Medical Center in New York City.

Dr. Ladapo presented the findings here at the North American Menopause Society 2013 Annual Meeting.

"There are wins on the patient side and wins on the physician side," he told Medscape Medical News. "Compared with regular stress testing, this test is actually much more sensitive. It functions very well as a rule-out test and was associated with a 22% savings in cardiac diagnostic costs," said Dr. Ladapo.

"Personalized, individualized medicine, including diagnostic strategies, is the way to go in the future," Peter Sinnaeve, MD, from the University Hospitals Leuven in Belgium, told Medscape Medical News. "Corus CAD is a simple test, and doesn't require exposure to radiation. Unfortunately, the test is expensive, but this small analysis does confirm that using it can reduce the cost of a work-up by 22%," said Dr. Sinnaeve, who was not involved with the study, but has published similar research (PLoS One. 2009;4[9]:e7037).

There are wins on the patient side and wins on the physician side.

Results from the recently published IMPACT trial (Crit Pathw Cardiol. 2013;12:37-42), as well as the COMPASS (Circ Cardiovasc Genet. 2013;6:154-162) and PREDICT (Ann Intern Med. 2010;153:425-434) trials, have demonstrated the clinical utility of the gene-expression test, Dr. Ladapo reported.

The sensitivity of the test in COMPASS and PREDICT was 89% and 85%, respectively, and the negative predictive value was 96% and 83%, respectively, for ruling out CAD.

In the IMPACT trial, diagnostic recommendations for 57 women (mean age, 53 years) made before the gene-expression test were changed for 34 women after the test. The intensity of diagnostic testing recommendations was reduced in 31 (91%) of these women and increased in 3 (9%), Dr. Ladapo said.

In his economic analysis of the IMPACT data, Dr. Ladapo found that 58% of women with low gene-expression scores (15 or less) had their diagnostic testing recommendations decreased, whereas 43% of those with higher scores had their testing recommendations increased.

The per patient cost was 22% lower for women with symptoms of CAD who underwent gene-expression testing than for a commercially insured matched cohort of women in a large national health claims database who underwent diagnostic testing ($1960 vs $2504).

This $544 difference did not reach statistical significance, but probably would have with larger numbers, said study coinvestigator Mark Monane, MD, who is chief medical officer for CardioDx.

"The list price for the test is $1245," Dr. Monane told Medscape Medical News. He explained that the per person cost of $1960 in the study included costs for follow-up procedures in some patients.

"It is not a statistically significant difference, but it is a clinically meaningful one when you consider the cost of radiation-induced cancer, contrast reactions, and multiple visits. And $500 does make a difference to some patients," he added. Although the test is covered by Medicare, the company is still in discussions with private insurers, he explained.

Each year, roughly 3 million nondiabetic stable patients present to primary care physicians or cardiologists with symptoms suggestive of CAD, said Dr. Ladapo.

Initial noninvasive CT angiography is often repeated, "which has received a lot of attention recently because of the high doses of radiation many patients are being exposed to," he said. For some patients, this is followed by invasive angiography, "a procedure that is costly and with significant risks. Most surprisingly, 60% of patients at this point have no evidence of obstructive coronary artery disease" (N Engl J Med. 2010;362:886-895).

The gene-expression test has not been linked to a risk for myocardial infarction or death, only to the presence of a significant coronary stenosis, Dr. Sinnaeve pointed out. "It is unclear — and unlikely — that using this test will improve outcomes in young to middle-aged women. But, if confirmed in larger prospective studies, it could reduce the cost of a work-up when significant obstructive CAD is suspected and, importantly, would reduce exposure to radiation in this population."

Dr. Ladapo is a consultant for CardioDX. Dr. Monane is chief medical officer of CardioDX. Dr. Sinnaeve has disclosed no relevant financial relationships.

North American Menopause Society (NAMS) 2013 Annual Meeting: Abstract S1. Presented October 10, 2013.

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