Maria Grana asks, who uses the ecarin clotting test? Can the ecarin clotting test be used for bivalirudin (Angiomax) monitoring? Is the ecarin clotting test FDA approved? We are having complaints from MDs that the activated clotting time (ACT ) is not responding to administration of heparin on some patients. Can these patients have antithrombin (AT , ATIII ) deficiency? Some of these patients are on Angiomax but the ACT is not FDA approved for angiomax monitoring and the package insert for the I-STAT says that other anticoagulants/drugs on board can interfere. Thank you for your help.
Hello, Maria, and thank you. The ecarin clotting time assay is available from Esoterix Coagulation, a LabCorp Company, and is offered for investigational or research use only. It is not FDA-approved, and for that reason I know of no local laboratories that offer the assay. Diagnostica Stago, Inc. has developed their Ecarin Chromogenic Assay, which may be used to measure the direct thrombin inhibitors (DTIs) Angiomax, Argatroban and the direct oral anticoagulant, dabigatran (Pradaxa), however it, too awaits FDA approval, though it has been available for several years in Europe. Aniara offers the Hyphen Biomed Hemoclot Thrombin Inhibitor assay, which is a plasma-diluted thrombin time. It may also be used to measure all three DTIs, however it, too, awaits FDA approval. The only assay that is currently FDA-approved for measuring any of the three DTIs is the PTT , which is also prolonged by heparin, and thus not useful when heparin and Angiomax are used together. The PTT results vary considerably by reagent manufacturer and by coagulometer, so it must be applied cautiously.
In instances when the ACT or the PTT do not appear to respond to heparin therapy, the first consideration is AT depletion, which may occur after a few days of heparin therapy. Congenital AT deficiency is rare, but may cause the same problem, sometimes called heparin resistance. The physician may order AT activity levels and, if necessary, administer AT concentrate.
By coincidence, Lesa Nelson just sent a question about ACT response to heparin that may help, I've linked her post here. I'm sorry I can't offer definitive assistance, the best we can hope for is speedy FDA intestigation of these well-defined new assays.