Importance of Fibrinogen Testing
Fibrinogen testing is critically important for rapidly identifying fibrinogen-associated hemostasis disorders in bleeding patients, enabling timely targeted replacement therapy that can reduce blood loss, decrease transfusion requirements, and potentially improve mortality outcomes.
Primary Clinical Applications
Bleeding Management
- Monitoring fibrinogen levels in bleeding patients is a reasonable measure to quickly recognize fibrinogen-associated hemostasis disorders 1
- Fibrinogen concentrate may reduce red cell transfusion requirements in cardiac surgery, and restoring physiological fibrinogen levels in bleeding patients may improve hemostasis 1
- Low plasma fibrinogen concentrations are associated with increased bleeding risk due to impaired primary and secondary hemostasis 2
Diagnostic Utility
- Fibrinogen testing differentiates between hypofibrinogenemia (low levels) and dysfibrinogenemia (abnormal function), which have distinct clinical implications 2
- Routine coagulation testing and specialized laboratory investigations guide diagnosis in patients suspected of having fibrinogen abnormalities 3
- Fibrinogen is essential for fibrin clot formation, and disorders in concentration or function are variably linked to bleeding and/or thrombosis risk 4
Testing Methodologies and Clinical Context
Standard Laboratory Testing
- Clotting rate assays (Clauss assay) remain the routine method of choice for investigation, monitoring, and treatment of bleeding disorders associated with low plasma fibrinogen 2
- However, the Clauss assay has substantial limitations in cardiac surgery with bypass due to large inter-assay variability, interference from high heparin levels, fibrin degradation products, and relatively long turnaround time 1
Point-of-Care Viscoelastic Testing
- Viscoelastic tests (FIBTEM in ROTEM or functional fibrinogen assay in TEG) provide rapid, standardized results and appear to have potential as the new reference standard in cardiovascular surgery 1
- These tests provide fair estimation of fibrinogen activity and contribution to clot formation even during cardiac surgery with bypass 1
- ROTEM FIBTEM shows better associations with the Clauss method (correlation 0.27-0.94) and more clinical use for monitoring fibrinogen deficiency than TEG functional fibrinogen (correlation 0-0.9) 5
Clinical Decision Thresholds
Cardiac Surgery Context
- A maximum clot firmness (MCF) in FIBTEM ≤4-6 mm should be considered a reasonable trigger for fibrinogen replacement in bleeding patients 1
- MCF of 6-8 mm represents a "grey zone" where fibrinogen replacement may be considered 1
- In post-bypass bleeding, maintaining physiological plasma fibrinogen levels (>9 mm MCF in FIBTEM) is crucial, but evidence does not support aiming for supranormal levels (>14 mm MCF) 1
General Bleeding Management
- For non-cardiac surgery bleeding, empiric fibrinogen concentrate (1-4g) should be administered when clinical bleeding is present, followed by coagulation testing to guide further therapy 1
- Once results are available, it is reasonable to maintain fibrinogen levels over 1.5 g/dL (150 mg/dL), which is necessary for clot formation and platelet aggregation 1
Additional Clinical Significance
Cardiovascular Risk Assessment
- Fibrinogen is a classical positive acute-phase reactant protein and an independent predictor of coronary heart disease events 2
- Immunoassays are useful for assessing cardiovascular risk and acute-phase reactions 2
Transfusion Guidance
- In cardiac surgery, fibrinogen testing likely results in reduction of blood loss (mean difference -88 mL) and may reduce need for RBC transfusion (risk reduction 18%), plasma transfusion (risk reduction 10%), and platelet transfusion (risk reduction 10.5%) 1
- TEG and ROTEM functional fibrinogen tests play important roles in diagnosis of fibrinogen-related coagulopathy and guidance of transfusion requirements 5
Important Caveats
Test Selection Considerations
- Viscoelastic tests should be combined with other assays to cover a range of hemostatic disturbances 1
- Results from TEG and ROTEM are correlated but not interchangeable between the two systems 5
- Prothrombin-time derived fibrinogen assays show wide variation with analyzers and reagents, demonstrate discrepancies with clotting rate assays, and are not recommended for routine clinical use 2
Pediatric Considerations
- Lower incremental in vivo recovery, faster clearance, and shorter half-life are observed in children aged 1 to <12 years, potentially requiring higher fibrinogen doses in this age group 6