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Specimen Management in Fibrinolysis

I had the opportunity to become reacquainted with Jennifer JacobsenMLS (ASCP),Allina Health Laboratories, Minneapolis, while attending the Mayo Laboratories Coagulation Testing Quality conference in Rochester, Minnesota August 7–10. Jennifer has this question about specimen management on patients being treated with tissue plasminogen activator (TPA, Activase®, Alteplase®):

George, both the prescribing information for Alteplase and Stago’s fibrinogen reagent package insert state that samples for coagulation testing from patients receiving TPA therapy should be collected in an anticoagulant containing an anti-plasmin agent such as aprotinin. Do you know of any lab that follows this recommendation? It seems to make logical sense that TPA would remain active in vitro and potentially interfere with clot-based assays, just as unfractionated heparin or a direct thrombin inhibitor would do.

Thank you for your question, Jennifer, and no, I do not know of any laboratories that use aprotinin to treat TPA patient specimens. Let’s watch for comments from participants.

In support, Jennifer also quoted the Activase and Stago fibrinogen package inserts:

“During Activase therapy, if coagulation tests and/or measures of fibrinolytic activity are performed, the results may be unreliable unless specific precautions are taken to preventin vitro artifacts. Activase is an enzyme that when present in blood in pharmacological concentrations remains active under in vitro conditions. This can lead to degradation of the fibrinogen in blood samples removed for analysis. Collection of blood samples in the presence of aprotinin (150–200 units/mL) can to some extend mitigate this phenomenon.”

And from Stago’s fibrinogen package insert, under Limitations:

“When the fibrinogen assay is to be performed in samples collected from patients receiving thrombolytic therapy, the blood samples must be collected with an anticoagulant mixture containing a plasmin inhibitor (such as aprotinin).”

By the way, a quick check on the Becton-Dickinson Vacutainer site reveals they market BD Pharmingen, a “Protease Inhibitor Cocktail.”

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