Background: The interfering effects of new anticoagulant agents targeting thrombin on fibrinogen assay has not been completely resolved. Reptilase time screens for fibrinogen abnormality similar to the thrombin time, but uses batroxobin to form fibrin clot and is not affected by most thrombin inhibitors, including heparin derivatives, dabigatran, and hirudin derivatives.

Aims: We designed a batroxobin based method to measure fibrinogen and evaluated basic aspects of assay performance.

Methods: We conducted reptilase time assays on standard plasma calibrators. We fitted Gompertz function functions to replicate each clotting curve of reptilase time. From each clotting curve function, we took alpha, calculated maximum of first and second derivatives (max1 and max2) and reptilase time to prepare the calibration curve and formula. We named the fibrinogen values derived from those parameters and Clauss method as FIB_rept-α, FIB_rept-max1, FIB_rept-max2, and FIB_Clauss. Then, we compared FIB_rept-α, FIB_rept-max1, FIB_rept-max2 with FIB_Clauss. We found FIB_rept-α values were comparable to FIB_Clauss.

Results: The within-run coefficient variations of FIB_{rept- α} at the fibrinogen levels of 216 and 307 mg/dL were 1.6% and 1.2%. The linearity of FIB_{rept- α} was kept from the high level of 400.7 mg/dL to the low level of 75.7 mg/dL. A comparison study was performed with 182 blood samples by measuring FIB_{rept- α} and FIB_Clauss. In this, were included blood samples from 30 patients on heparin therapy, 72 on low molecular heparin (36 on dalteparin and 36 on enoxaparin. FIB_{rept- α} and FIB_Clauss showed good correlation (correlation coefficient =0.96). We determined the effect of bivalirudin, heparin, low molecular heparin and dabigatran on FIB_{rept- α} and FIB_Clauss. FIB_Clauss falsely decreased at low level of bivalirudin (1.6 mg/dL). FIB_{rept- α}showed no interfence of bivalirudin, heparin, low molecular heparin and dabigatran.

Conclusions: Our reptilase time based fibrinogen assay was well correlated with Clauss method and not interfered by thrombin targeting anticoagulants.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/batroxobin-based-method-to-measure-fibrinogen-to-overcome-interfering-effects-of-new-anticoagulant-agents-targeting-thrombin/