For some cardiac patients, recovery from a common heart procedure can be complicated by a single gene responsible for drug processing. The risk could be lowered with the first bedside genetic test of its kind. The test shows promise for quickly and easily identifying patients who need a different medication.
After a patient receives a heart stent—a small scaffold that props open an artery—his or her doctor will prescribe a blood thinner to prevent platelets from building up inside the device. However, for some 70 percent of patients with Asian ancestry and 30 percent of patients with African or European ancestry, a single genetic variant will prevent one of the most commonly prescribed blood thinners from working. Alternatives exist, but they are more expensive, so hospitals could use an easy way to identify who does and does not need the more expensive drug.
Canada’s Spartan Bioscience has developed a near “plug-and-play” genotyping device that allows nurses and others to quickly screen patients at the bedside, perhaps while they are undergoing the stent placement procedure. Users take a DNA sample from a patient’s cheek with a specialized swab, add the sample to a disposable tube, and then place the tube and sample in a proprietary shoebox-sized machine and hit a button. Shortly thereafter, the user receives a printout of the patient’s genetic status for the drug-processing variant. The whole procedure takes about an hour. Most clinicians currently have to wait several days for similar information to come from off-site genetics testing companies.
“For six years we’ve been plugging away at this, and we finally broke through about a year and a half ago,” says Spartan Bioscience founder Paul Lem. He says the simple test came to life with innovations at every step—from the special swab that collects the right amount of DNA, to the chemicals in the disposable reaction tube, to the software that automates the DNA reading—and a team with diverse backgrounds including his in medicine and molecular biology and others’ in optical hardware.
Lem has kept an eye on other companies trying to create a bedside genetic test, some going after the same variant, and calculates that over $1 billion in capital has been spent over the last five years in this area.
The University of Ottawa Heart Institute researchers conducted a proof-of-principle trial for the device and found that the bedside test is effective at quickly identifying carriers of the drug-processing variant and can be performed by nurses with minimal training. The findings were published in The Lancet last week.
“The stakes are pretty high” for the risks associated with the variant in the test, says Euan Ashley, a cardiologist with Stanford’s Center for Inherited Cardiovascular Disease. Patients who receive a stent implant after a heart attack or as a preventive measure are at risk for serious adverse events if their bodies cannot process a commonly prescribed anti-platelet drug into its active form. “There’s a startling number of people who carry the variant, which leaves them at risk,” says Ashley. “Being able to get an answer within an hour or two—when you are thinking of a patient’s heart—is a pretty compelling case for [testing for it].”
Ashley notes that there may come a day when a patient’s entire genome could be sequenced at the bedside, which may encourage a different model for bedside genotyping. “But we aren’t there yet,” he says. Genome-sequencing technologies capable of clinical diagnoses currently require days to identify all the base pairs in a human genome. “Sometimes, speed is of the essence,” says Ashley. The technology is a good example of a real opportunity to do actual personalized medicine in real time, he says.
Spartan Bioscience got regulatory approval for the test in the European Union in December 2010, and hopes to have approval in the United States by the end of this year. The company gives away the devices for free, and charges $200 per test.
Spartan Bioscience is also looking for other applications for the technology, says Lem, from infectious diseases like MRSA, an antibiotic resistant strain of staph infections, to pharmacogenetic markers such as a hereditary resistance to standard hepatitis C treatment.
“Doctors from around the world have been pinging us with all the applications they’ve been saving up to the day when a bedside DNA test is finally available,” says Lem.
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