Thinking that stroke is something one’s parents or grandparents most likely to suffer, rather than the middle-aged, is no longer a very good assumption.
One of healthcare’s so-called “inconvenient truths” — to borrow a phrase from Al Gore — is that “many people still don’t realize” that a third of strokes afflict people in the 45 to 64 age group, Richard Lanman, MD, chief medical officer for diaDexus (South San Francisco), told Diagnostics & Imaging Week.
To help stem the tide of that growing trend is the PLAC test, from diaDexus, which measures lipoprotein-associated phospholipase A (2) (Lp-PLA (2)). And the company yesterday reported the results of a new study indicating that Lp-PLA (2), a specific indicator of vascular inflammation, provides information over and above traditional risk factors — such as smoking and high blood pressure — to help identify individuals at the highest risk for ischemic stroke.
The PLAC test was cleared for marketing in coronary heart disease in 2003 and was the biotechnology company’s first FDA-approved product.
Results of the new study were recently presented at the 18th annual scientific sessions of the Society for Vascular Medicine and Biology (Northbrook, Illinois) in Baltimore.
Lanman said that when he got out of medical school stroke did, in fact, tend to strike older adults. But the rise of obesity and, consequently, such things as metabolic syndrome — also now often being referred to as “diabesity” — leads to belly fat which in turn leads to inflammation.
“The people who get a lot of fat on their bellies ... they start to get rising blood sugar, they [develop] problems with their good cholesterol – all these things contribute to stroke,” Lanman said. “Also, that abdominal fat is not inert; it gets inflamed.”
And when the plaques on the artery walls become inflamed, they burst, leading to stroke, one of the most debilitating long-term healthcare issues in those cases where the patient survives.
Christie Ballantyne, MD, of Baylor College of Medicine (Houston), led the prospective case cohort study of 12,762 apparently healthy middle-aged men and women in the Atherosclerosis Risk in Communities (ARIC) study.
The researchers evaluated patients using traditional risk factors for stroke, such as age, sex, race, smoking, blood pressure, cholesterol levels, diabetes and body mass index. They then categorized the risk levels of those patients as low, moderate and high.
Then the researchers measured levels of the inflammatory indicators Lp-PLA(2) and C-reactive protein (CRP) to determine if the biomarkers helped further classify patients’ five-year risk for stroke.
diaDexus said the results showed that the addition of Lp-PLA(2), as measured by the company’s PLAC test, and CRP significantly improved stroke risk assessment by reclassifying 37% of the moderate-risk category, as opposed to relying on traditional risk factors alone to make an estimation.
“Traditional risk factors my not be quite as good for predicting stroke as they are for heart attack,” said Ballantyne in a statement. “By using these simple, noninvasive blood tests, we may be able to do a better job determining those patients who need to take their stroke risk very seriously.”
Lanman said that his hope is that these new study results will help in educating physicians and patients about stroke risk among those who would be considered to be at moderate risk by traditional factors.
He said also that for some people, having the PLAC test and finding themselves at higher risk than previously assumed might give them time to “clean up their act” through the use of statin drugs – some of which have gone generic and therefore less expensive – along with diet and exercise.
The PLAC test has been cleared for marketing by the FDA as an aid in predicting risk for coronary heart disease and ischemic stroke associated with atherosclerosis.
Autopsy results show that 85% of people in the U.S. have significant thickening of the arteries by the time they reach 50, and that atherosclerosis can begin in the teenage years.
Earlier this year, diaDexus reported receiving a U.S. patent on its PLAC test for both stroke and heart attack assessment.
diaDexus was born as a spinout of SmithKline Beecham (now GlaxoSmithKline; London) in 1997 as part of a joint venture with Incyte Genomics (Palo Alto, California) with its focus on diagnostics.
Speaking at the JP Morgan Healthcare Conference in San Francisco in January, Patrick Plewman, president/CEO of diaDexus, noted that the company’s opportunities advanced with the grant of a CPT code from Medicare for the test at $47, as compared to a year before when the government was reimbursing the test at only $18.
“Reimbursement is there, [and] the economic incentive is there to allow the labs and distributors to get behind this test,” Plewman said at the conference.
The company is also developing a pipeline of cancer diagnostics.