Accumetrics (San Diego) President and CEO Rob Hillman says there are about 25 million people on an aspirin regimen to prevent platelet aggregation in blood vessels as a way of preventing heart attack or stroke.

But that strategy does not always work, particularly in those patients who are aspirin-resistant, a condition that the company said previous studies have shown is associated with triple the risk of heart attack, stroke and death.

New studies reported at the annual scientific sessions of the American College of Cardiology (ACC; Bethesda, Maryland) in Orlando, Florida, earlier this week confirm that up to 27% of aspirin users with coronary artery disease are resistant to aspirin's antiplatelet effects. The studies also showed that those most likely to be aspirin-resistant are women, the elderly and those taking lower doses of aspirin.

Furthermore, the research indicated that resistance to aspirin and clopidogrel, known by the brand name Plavix, may occur together. That was determined by studying patients undergoing coronary procedures, such as percutaneous coronary intervention.

So, other than the predictors of aspirin resistance mentioned above, how does a doctor know that a patient is going to be aspirin-resistant before relying on that all-purpose over-the-counter drug to prevent further cardiovascular problems?

Accumetrix thinks it has the answer in the VerifyNow Aspirin Test, for which the company just last week received a CLIA waiver for what Hillman calls a "new, improved version" of the test. The diagnostic test was initially approved by the FDA in 2003.

"What all that means is that it is now available for use in doctor's offices around the country and is a much improved version over the original," Hillman told Medical Device Daily.

The ability to test the antiplatelet effect of aspirin on a particular patient existed before Accumetrics came out with its test, he said. However, that test had to be done in a lab by a skilled technician and required up to an hour and a half before results were available.

With the VerifyNow Aspirin test, the company has whittled the time it takes to get results down to about 10 minutes.

"What the test basically does is if you take a tube of blood from the patient, you place it into our assay device, which automatically samples the blood, mixes it with reagents that are already in the assay device," and the container in which the assay device sits "reads out the level of aggregation," Hillman said.

All the reagents are calibrated at the factory, as well as bar codes and other controls. The company said that the device weighs about four pounds and is compact and portable.

Hillman said "a large number" of the people who are using the test are clinical cardiologists and physicians focused on internal medicine, "largely based on awareness."

The company said the test is covered by medical insurance and Medicare plans with a CPT code, and can be ordered by any physician.

To market the test, Accumetrics is working with two companies. On the physician side, the company is working with Physician Sales and Services (PSS; Jacksonville, Florida), which Hillman estimates has about 1,000 reps who are in physicians' offices every day to handle, among other needs, laboratory testing products.

On the hospital side, Accumetrics uses Fisher HealthCare (Hampton, New Hampshire), which markets to large hospitals and the labs within those hospitals, Hillman said.

"We do that in coordination with a very focused group of sales people that we have that work with these large distribution networks," he said.

The results presented at ACC this week were based on research reported by W.H. Chen and colleagues at the University of Hong Kong that involved 468 patients. Women, the elderly, those with renal insufficiency, low hemoglobin levels and those taking low-dose aspirin were found to have the highest likelihood of being aspirin resistant.

The authors found that dosage of aspirin resistance was associated with the prevalence of aspirin resistance. The highest prevalence of aspirin resistance was associated with doses of less than 100 mg, which include 30.2%, was less prevalent in higher aspirin doses of 150 mg, or 16.7% and non-existent with 300 mg (0%).

Separately, a meta-analysis of 200,000 people also presented at the ACC meeting showed that risk of bleeding increases with increasing doses of aspirin.

"In combination, these two studies suggest that a balance between safety and effectiveness needs to be achieved so that the lowest, effective dose is prescribed and patients are confirmed responsive to their aspirin regimen," the company said.

"Knowledge of particular patient groups susceptible to aspirin resistance underscores the need to confirm aspirin response so that alternative or additional antiplatelet therapy can be considered in this population at higher risk," Daniel Simon, associate director, interventional cardiology at Brigham and Women's Hospital and professor of medicine at Harvard Medical School (both Boston), said in a statement. "Physicians don't use coumadin or heparin without monitoring their anti-thrombotic effects. Antiplatelet therapy is no different. It is clear that the individual patient responds differently and one dose does not fit all."