Coag tests get tweaked

Oct. 1, 2010

While no one can dispute the importance of coagulation tests for the care and treatment of patients in the critical-care unit and surgical suite, the finite number of tests regularly being used has become standards. But that appears to be changing as new assays hit the market and new anticoagulation drugs gain a wider acceptance.

Heather DeVries, senior medical technologist at Clarian Pathology Laboratory in Indianapolis, IN, which is owned by Clarian Health Partners, says her lab is now running three new coagulation tests that use new assays. One is for heparin monitoring; one checks for lupus anticoagulants (silica clotting time test); and one is specifically designed for patients taking Plavix.

The increased use of low-dose aspirin to prevent heart attacks has led Broomfield, CO-based Corgenix Medical Corp. to develop an assay that helps determine whether this therapy is having the desired effect. “It has been shown that up to 25% of patients on low-dose aspirin do not respond to the therapy,” says Denise Taylor, marketing manager. She explains that the new assay measures levels of 11-dehydro thromboxane B2 which allows platelets to clump and which is secreted in the urine. Cleared by the U.S. Food and Drug Administration (FDA) in 2007, this assay is now being used in large reference labs, she says.

The benefits of this test are numerous, Taylor says. “It allows the physician to individualize therapy.” And because it uses random urine samples, these samples can be frozen and batched, whereas the traditional blood test must be run within four hours of draw, she notes.Although this urine test takes about three hours to perform, Taylor says future refinements could make this another point-of-care test (POCT).

Robert Trinka, director of Sales and Marketing for American Diagnostica Inc. (ADI) in Stamford, CT — a subsidiary of Tokyo, Japan-based Sekisui Medical Co. Ltd — says, “We are known for our testing for lupus anticoagulants, which is a screening test for antiphospholipid syndrome, or APS. And we are one of the few manufacturers of the dilute Russell's viper venom time test (dRVVT) in the world.

“We have also pioneered a commercial test for the dilute prothrombin time test, or dPT test, which measures lupus anticoagulants from the external pathway of the coagulation cascade. This test previously was called the TTI test (tissue thromboplastin inhibition assay). The dPT and TTI tests have been performed as home-brew tests by laboratories for many years. ADI has commercialized this test, also adding a high-phospholipid confirmatory reagent as required by International Society on Thrombosis and Haemostasis, or ISTH, guidelines and manufacturing under current good manufacturing practices, or cGMP, guidelines.”

Trinka points to a greater acceptance of the dPT test as more and more physicians realize the value of the test. “Study after study has shown that the dPT test is required to find lupus- anticoagulant patients that the other tests (e.g., dRVVT and lupus sensitive aPTT test) do not find. A study at Duke University Medical Center, prospectively, concluded that all three tests — dRVVT, LS aPTT and dPT — must be run to find all lupus-anticoagulant patients.”

As for other trends in the coagulation-testing field, Trinka says, “We are seeing increased demand for tests to perform ADAMTS13 assays to diagnose TTP. I believe that ADAMTS13 testing has grown more than fourfold since 2000.

“And we see increased use of chromogenic heparin anti-FXa testing calibrated for low-molecular-weight heparins … also the use of chromogenic assays to replace clotting assays … wider use of therapeutic anticoagulants (e.g., warfarin and others) distorts the results from clotting assays.”

With many laboratory tests moving to the molecular level, hemostasis is following suit. Curtis Knox, product manager for Cystic Fibrosis and Coagulation/Thrombophilia Molecular Diagnostics at Hologic. in Madison, WI, says his company has developed four molecular tests to measure factors II and V as well as MTHFR 677 and 1299. All four tests measure a patient's risk for developing blood clots (thrombophilia).

Using a proprietary chemistry platform developed at the University of Wisconsin, these tests look for specific genetic markers (base changes in DNA) to evaluate genetic risk. “These genetic tests assess your risk, especially if you have already had a blood clot,” Knox says, adding that these tests are now being used in reference labs and in hospital labs that have the capability to perform molecular tests.

Knox sees molecular tests continuing to be a major trend. But he also sees a trend toward pharmacogenetic testing which can determine, on the genetic level, how a person will respond to a specific anticoagulant.

The trend toward point-of-care testing is not new for coagulant tests. The activated clotting time, or ACT, test has been an accepted POCT for about 30 years. But today's trend is to offer nurses lab-like results in a more portable device that leads to faster results, connectivity with the laboratory information system (LIS), and built-in safeguards to reduce errors.

In July, Roche Diagnostics Corp. in Indianapolis, IN, announced it had received FDA clearance for its next-generation anticoagulation-testing device that includes an integrated bar-code reader. The bar-code reader can capture both operator- and patient-identification information to help ensure patient safety. In addition, this meter also uses built-in quality controls and gives operators the option to run two levels of additional external liquid controls when they are required to comply with the facilitiy's regulatory policy, says Tim Huston, director of marketing, Professional Diagnostics.

Bobby Sharp, group marketing manager, Professional Diagnostics, says the addition of this meter to Roche's family of coagulation monitors continues the trend toward POCT. “PT/INR (prothrombin time/international normalized ratio) testing is moving out of the lab to the point-of care. The faster turnaround time allows a physician to adjust coagulation therapy within minutes of the test.”

This system/meter also benefits patients when used in a doctor's office, says Huston. In that setting, the physician has the ability to adjust anticoagulation medications in order to keep the patient within the therapeutic range while the patient is still sitting in the office.

“It is better for the patient; better for the physician, and more cost efficient,” Huston says.

The new meter requires only an eight-microliter sample of blood and provides test results in about a minute. It can store up to 1,000 patient results; and, by using an MAS module that also is available from Roche, can automatically transfer these results to an LIS or electronic health record, Huston says.

Richard R. Rogoski is a freelance journalist based in Durham, NC. Contact him at [email protected].