Resolving Bivalirudin Interference on Fibrinogen Testing by the Use of Activated Carbon

BACKGROUND: Direct thrombin inhibitors may lead to falsely low fibrinogen results. The interference of bivalirudin on fibrinogen assays has not been thoroughly evaluated. This study investigates the interference of bivalirudin on fibrinogen detection and the potential use of activated carbon to address this issue. METHODS: Normal pooled plasma from 20 healthy subjects was spiked with increasing bivalirudin concentrations (0-6.4 μg/mL). Interference of bivalirudin on fibrinogen testing was evaluated by comparing three Clauss-method assays (HemosIL Fibrinogen-C XL; STA-Fibrinogen; Dade Thrombin) to an immunoassay (N Antiserum to Human Fibrinogen reagent, NAHF). Activated partial thromboplastin time (APTT) and fibrinogen results were analyzed before and after the addition of activated carbon (AC) to evaluate the absorption of bivalirudin by AC. RESULTS: The NAHF immunoassay remained unaffected by bivalirudin (p = 0.27). All three Clauss-methods assays showed a significant downward trend with the increase of bivalirudin concentration (STA-Fibrinogen: p = 0.012, Dade Thrombin: p < 0.001, Fibrinogen-C XL: p < 0.001). When compared to their respective baselines, STA-Fibrinogen exhibited a reduction of 16%, Dade Thrombin showed a reduction of 40%, and Fibrinogen-C XL displayed a decrease of up to 89%. Neither STA-Fibrinogen nor Dade Thrombin displayed a significant downward trend when the APTT ratio did not exceed 2.5. After the addition of AC, SynthASil APTT and HemosIL Fibrinogen-C XL levels of all samples containing varying concentrations of bivalirudin returned to near baseline. CONCLUSION: The influences of bivalirudin on fibrinogen assays vary significantly. Activated carbon can effectively remove bivalirudin from plasma, thereby eliminating its interference on fibrinogen testing.