Quest Diagnostics' DNA testing for gene variants help improve outcomes for stent recipients

DNA testing for gene variants that can increase the risk of major coronary events in certain patients taking the anti-clotting drug Plavix® (clopidogrel bisulfate) is now being performed by Quest Diagnostics (NYSE: DGX) for Scripps Health patients electing to undergo coronary stent procedures. Scripps Health is believed to be the first health system in the U.S. to deploy this genetic testing service for coronary stent patients as part of patient treatment. Scripps physicians will initially offer the genetic tests to elective stent patients before they undergo their procedures at Scripps Green Hospital in San Diego.

The Quest Diagnostics test is designed to help improve outcomes for stent recipients by enabling Scripps Health cardiologists to personalize therapy based on diagnostic insights into a patient's genetic makeup.

"Our collaboration with Quest Diagnostics represents a landmark program in individualized medicine, based on considerable new data and new choices for one of the most commonly prescribed medications and medical procedures in the world," said Dr. Eric Topol, chief academic officer of Scripps Health. "This program demonstrates Scripps Health's commitment to being at the forefront of individualized cardiovascular medicine."

Most of the one million patients who undergo stent procedures in the U.S. each year receive Plavix to help prevent blood clots that can cause heart attacks and strokes. Yet, large-scale, peer-reviewed studies demonstrate that patients with one or more mutated alleles (variants) of the Cytochrome (CYP) 2C19 gene are unable to respond properly to Plavix, increasing their risk of death, heart attack or stroke compared to people with normal alleles. About one third of people of Caucasian descent, and 40 percent or more of people of African and Asian descent, possess common polymorphisms in the CYP2C19 gene.

The Quest Diagnostics test is believed to be the first provided by a national laboratory to combine testing for the normal version of the CYP2C19 gene and four mutations that appear in the genetics of 90 percent of Caucasians and 99 percent of Asians who are poor metabolizers of clopidogrel. Specifically, the test, which employs polymerase chain reaction (PCR), indicates if a patient will respond normally to clopidrogel (has the wild type, or normal, CYP2C19*1 allele) or not normally because of the presence of one or more of four mutated alleles (CYP2C19*2, CYP2C19*3, CYP2C19*4 or CYP2C19*5).

The saliva-based test allows specimens to be collected at a physician's office or by the patient in his or her home. It is the first saliva-based test for cardiovascular disease developed by Quest Diagnostics. The company expects to offer the saliva- and blood-based versions of the test nationally to its other clients this month.

Patients who test positive for the mutated alleles may receive alternative treatments based on a variety of factors. These treatments may include increased monitoring, an increased dosage of clopidogrel or the use of alternative therapies, including treatment with Effient® (prasugrel), a blood thinner approved by the FDA in July 2009.

"Our collaboration with Scripps Health reflects our commitment to developing diagnostics based on quality research and superlative medical expertise," said Jon R. Cohen, M.D., a former vascular surgeon who is now senior vice president and chief medical officer for Quest Diagnostics. "We look forward to continuing to work with Scripps to design forward-thinking diagnostics and medical practices that, like CYP testing, can have a significant favorable impact on patient outcomes."