MATTHEW PERRONE AP Business Writer WASHINGTON (AP) — "Just spit." With those simple instructions, health care providers in California are hoping to expand the use of genetic testing to make sure patients get the right medication. Scripps Health hospital system has begun using a saliva-based genetic test to detect whether patients will respond to Plavix, a widely used blood thinner that usually prevents clots. But recent studies show about one-third of people of European descent, and more than 40 percent of people of African and Asian descent don't properly respond to Plavix, putting them at increased risk of fatal blood clots. The new laboratory test from Quest Diagnostics detects four genetic mutations found in more than 90 percent of patients who won't benefit from the drug, which is marketed by Bristol-Myers Squibb and Sanofi-Aventis. While older tests were capable of picking up the mutations, Quest says its test is the first designed for routine use and quick processing. "It's so much simpler for patients because they don't have to undergo a blood draw, and that makes the process much more convenient for everyone involved," said Dr. Eric Topol, chief academic officer of Scripps Health. San Diego-based Scripps will initially offer the test to all patients receiving a stent, a metal tube used to prop open arteries after they have been cleared of fatty plaque. Plavix is commonly prescribed to prevent deadly blood clots from forming on the metal. Patients who don't respond to Plavix can be given alternate treatments, such as Eli Lilly's blood thinner Effient. Besides saving lives, Topol said the saliva test could help cut costs by avoiding wasteful dispensing of unnecessary drugs and preventing catastrophic — and costly — events like heart attack and stroke. Plavix was the third best-selling drug in the U.S. last year with sales of $4.8 billion, according to health research firm IMS Health. Proponents of genetic testing have long claimed it would usher in an era of personalized medicine, in which medical treatment is based on the patient's genetic code. There are several tests in use to gauge how patients will respond to cancer treatments, such as Genentech's breast cancer drug Herceptin. But the technology has yet to find application in broader fields like cardiology. "Hopefully we'll build on this by taking really exciting genetic discoveries and making them part of routine practice to improve care for patients," said Topol. Madison, N.J.-based Quest expects to launch the saliva test nationally later this month. The test will cost around $200, according to the company, compared with $700 for older diagnostics which test for a much wider array of genetic indicators. Quest is still calculating the potential market for its so-called CYP2C19 test, which is named after the gene it targets. But the company noted that gene-based diagnostics accounted for 20 percent of revenue last year, or about $1.5 billion.