Click here for an open-access 2026 article comparing the time-honored Clauss fibrinogen assay with the PT-derived assay: Latona A, Hill K, Rane M, Ho A, Mitra B. Diagnostic accuracy of Clauss and prothrombin time-derived fibrinogen against rotational thromboelastometry FIBTEM-A5. Res Pract Thromb Haemost. 20266;10:103439. doi: 10.1016/j.rpth.2026.103439. PMID: 42027315; PMCID: PMC13100266.
Abstract
Background: Fibrinogen levels may fall early in major hemorrhage. The Clauss assay (Fib-C) is the laboratory gold standard, while the prothrombin time-derived assay (Fib-D) is a rapid, lower-cost alternative.
Objectives: To compare Fib-C and Fib-D with viscoelastic-derived clot firmness.
Methods: Data from all Queensland Health hospitals were extracted (2019-2025). Rotational Thromboelastometry FIBTEM-A5 was the reference standard. Paired Fib-C and Fib-D results with FIBTEM-A5 were analyzed. The primary outcome was correlation with FIBTEM-A5; secondary analyses assessed predictive performance for FIBTEM-A5 of ≤ 10 mm.
Results: Of 2208 paired results were included, Fib-C correlated more strongly with FIBTEM-A5 than Fib-D (r = 0.85 vs 0.82; P = .008) and had higher accuracy for FIBTEM-A5 of ≤ 10 mm (area under the curve, 0.92 vs 0.90; P < .05). Optimal thresholds for FIBTEM-A5 of ≤ 10 mm were 2.1 g/L for Fib-C and 2.3g/L for Fib-D (P < .05).For absolute fibrinogen values, Fib-D produced higher mean levels than Fib-C (overall, 2.3 vs 2.1 g/L; P < .05), with differences observed in trauma (2.4 vs 2.2 g/L; P < .05) and chronic liver disease (1.9 vs 1.7 g/L; P < .05).
Conclusion: Fib-C aligns more closely with viscoelastic clot firmness than Fib-D. These results support Fib-C as the preferred assay and discontinuing routine Fib-D reporting in critical bleeding.
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