Fibrinogen Measurement and Clinical Significance

Test Methodology

• The World Health Organization recommends the Clauss method as the standard approach for measuring fibrinogen, which works by adding excess thrombin to diluted plasma samples and measuring the time to clot formation, with results interpolated from a standard curve 1
• The Clauss method measures plasma fibrinogen concentration, with results expressed in g/L, and a normal reference range of 1.8-3.5 g/L or 2.0-4.0 g/L depending on the reagent used 3, 1

Clinical Significance

• Fibrinogen is the first coagulation factor to critically decrease during massive blood loss replacement, and levels <2 g/L are associated with significant bleeding risk in trauma patients 4, 2
• The Clauss method correlates with functional coagulation parameters, and fibrinogen levels <2 g/L have a 100% positive predictive value for progression to severe bleeding in postpartum hemorrhage studies 4, 2

Important Limitations and Pitfalls

• The Clauss method can significantly overestimate actual fibrinogen concentration in the presence of artificial colloids such as hydroxyethyl starch (HES), and reproducibility is impaired in patients after thrombolytic therapy or with disseminated intravascular coagulation 4, 2, 3, 1

Comparison with Alternative Methods

• Immunological assays measure total fibrinogen antigen concentration rather than the amount contributing to clotting, and viscoelastic point-of-care methods (FibTEM) may be preferable for guiding fibrinogen administration in acute bleeding scenarios 3, 1, 4, 2

Clinical Application

• Treatment with fibrinogen concentrate or cryoprecipitate is recommended when fibrinogen falls below 1.5-2.0 g/L in the setting of significant bleeding, as recommended by the World Health Organization 2