When is a fibrinogen test recommended for a patient with a history of bleeding or clotting disorders, or those at risk due to other medical conditions, such as liver disease or severe trauma?

Fibrinogen Testing in Bleeding and Clotting Disorders

Fibrinogen testing should be performed as first-line laboratory evaluation in all patients with suspected bleeding disorders, those with liver disease undergoing procedures, and in trauma patients with major hemorrhage. 1

When to Order Fibrinogen Testing

Bleeding Disorder Evaluation

• Order fibrinogen level as part of initial screening in any patient presenting with unexplained bleeding, alongside PT, aPTT, CBC with platelet count, and von Willebrand factor studies 1
• This first-line panel identifies the vast majority of clinically significant bleeding disorders 1
• Do not delay testing - fibrinogen is the first coagulation factor to reach critically low levels during massive hemorrhage 2, 3

Liver Disease Patients

• Measure fibrinogen before any invasive procedure in patients with cirrhosis, particularly when fibrinogen levels are suspected to be <100-150 mg/dL 4
• Fibrinogen levels <100 mg/dL (1.0 g/L) are associated with spontaneous and procedure-related bleeding in cirrhosis 4, 2
• However, routine correction of low fibrinogen to prevent procedural bleeding is discouraged - the association may simply reflect disease severity rather than causality 4
• The most agreed-upon threshold for fibrinogen replacement in actively bleeding cirrhotic patients is >120 mg/dL 4, 2

Trauma and Major Hemorrhage

• Perform repeated fibrinogen measurements in trauma patients with major bleeding, as fibrinogen reaches critical levels earlier than other coagulation factors 4, 3
• Target fibrinogen levels >200 mg/dL (2.0 g/L) for effective hemostasis in trauma patients without liver disease 4, 2
• In massive bleeding, fibrinogen levels <150-200 mg/dL indicate need for replacement 4, 3

Critical Thresholds for Interpretation

Bleeding Risk Stratification

• Normal range: 2.0-4.0 g/L (200-400 mg/dL) 2
• Significant deficiency: <1.5-2.0 g/L (150-200 mg/dL) - requires intervention in bleeding scenarios 2, 3
• Critically low: <1.0 g/L (100 mg/dL) - first coagulation factor to reach dangerous levels during hemorrhage 2
• Cirrhosis-specific threshold: <100 mg/dL - associated with spontaneous bleeding 4, 2

Elevated Fibrinogen

• Levels >4.0 g/L indicate inflammation, not bleeding risk 5, 2
• Elevated fibrinogen increases thrombotic risk, not bleeding risk 5
• Fibrinogen functions as an acute phase reactant during infection, inflammation, malignancy, and tissue injury 5, 2

Testing Methodology

Preferred Method

• The Clauss fibrinogen assay is the method of choice for assessing fibrinogen function 6
• This is the most frequently recommended laboratory technique 2

Important Caveats

• The Clauss method overestimates fibrinogen in the presence of artificial colloids like hydroxyethyl starch 4, 5
• PT-derived fibrinogen assays should be interpreted with caution - results are not interchangeable between methods and can overestimate fibrinogen in certain clinical scenarios 6, 7
• In dysfibrinogenemia, PT-derived assays may show values approximately four times higher than Clauss assay, potentially masking bleeding risk 7

Point-of-Care Testing

• Viscoelastic methods (TEG/ROTEM) may be preferable to laboratory fibrinogen measurement for guiding replacement therapy in emergency situations 4, 8
• These methods assess functional fibrinogen and can guide goal-directed therapy 8

When NOT to Test or Treat

Avoid Unnecessary Testing

• Do not test fibrinogen to assess procedural bleeding risk in patients without liver disease or active bleeding - standard coagulation parameters poorly predict bleeding in most scenarios 4

Avoid Inappropriate Treatment

• Do not prophylactically correct abnormal fibrinogen levels to prevent spontaneous bleeding in cirrhosis - this is not recommended 4
• Do not empirically treat elevated fibrinogen with plasma or fibrinogen concentrate - these are reserved for active bleeding with low fibrinogen (<1.5 g/L) 5
• Do not interpret elevated fibrinogen as a contraindication to procedures - elevation does not increase bleeding risk 5

Special Populations

Congenital Fibrinogen Disorders

• Perform both fibrinogen activity (Clauss) and fibrinogen antigen assays to distinguish quantitative from qualitative disorders 6, 9, 7
• Genetic testing is recommended for confirmation of congenital fibrinogen disorders 6
• Patients with congenital afibrinogenemia may be asymptomatic or even have thrombotic tendency, contrasting with predictable bleeding in hemophilia 4

Timing Considerations

• Delay testing for 48-72 hours after blood product transfusions to avoid misleading results 1
• Fibrinogen levels vary with stress, inflammation, pregnancy, and estrogen use 1