Unit Converter
Fibrinogen
(Key Coagulation Factor – Acute Phase Reactant, Bleeding Risk Marker & Thrombotic Indicator)
Synonyms
- Fibrinogen
- Factor I
- Plasma fibrinogen
- Coagulation factor I
- Fibrin clot precursor
Units of Measurement
- g/L
- mg/dL
- mg/100 mL
- mg%
- mg/L
- µg/mL
Key Conversions
1 g/L = 100 mg/dL
1 mg/dL = 10 mg/L
1 mg/L = 0.001 g/L
1 µg/mL = 1 mg/L
mg/dL = mg% = mg/100 mL
Description
Fibrinogen is a soluble plasma glycoprotein produced by the liver.
It is converted by thrombin into fibrin, which forms the structural mesh of blood clots.
Fibrinogen is essential for:
- Coagulation
- Platelet aggregation
- Wound healing
- Inflammatory response
It is also a major acute-phase reactant, rising significantly during inflammation and infection.
Physiological Role
- Final substrate of the coagulation cascade
- Cleaved into fibrin monomers by thrombin
- Stabilized by Factor XIIIa to form cross-linked fibrin clot
- Supports platelet adhesion through GP IIb/IIIa receptors
Clinical Significance
Low Fibrinogen (Hypofibrinogenemia / Afibrinogenemia)
Causes
- Liver Disease
- Cirrhosis
- Fulminant hepatic failure
- Cirrhosis
- DIC (Disseminated Intravascular Coagulation)
- Massive consumption of clotting factors
- Massive consumption of clotting factors
- Massive Bleeding / Trauma
- Congenital Disorders
- Afibrinogenemia
- Hypofibrinogenemia
- Dysfibrinogenemia
- Afibrinogenemia
- Dilutional Coagulopathy
- Massive transfusion
- Massive transfusion
Clinical Symptoms
- Prolonged PT / aPTT
- Poor clot formation
- Excessive bleeding
- Oozing from venipuncture sites
Fibrinogen <1.0 g/L (100 mg/dL) = high bleeding risk
Replacement needed (cryoprecipitate or fibrinogen concentrate)
High Fibrinogen (Hyperfibrinogenemia)
Often reflects inflammation, not clotting abnormality.
Causes
- Acute inflammation
- Chronic infection
- Trauma
- Pregnancy
- Smoking
- Metabolic syndrome
- Obesity
- Malignancy
- Post-surgery
- MI / stroke (risk marker)
Cardiovascular Risk:
High fibrinogen is associated with increased thrombosis risk.
Reference Intervals
(Tietz 8E + ISTH + Mayo + ARUP)
Adults
- 2.0 – 4.0 g/L
(or 200 – 400 mg/dL)
Pregnancy
- 3.0 – 6.0 g/L (physiologic increase)
Newborns
- 1.5 – 3.0 g/L
Critical Values
- <1.0 g/L → high bleeding risk
- >7.0 g/L → risk of thrombosis, hyperviscosity (rare)
Diagnostic Uses
1. Coagulation Assessment
- DIC
- Liver disease
- Massive bleeding
- Trauma-induced coagulopathy
2. Cardiovascular Risk
High fibrinogen associated with:
- MI
- Stroke
- Atherosclerosis
3. Monitoring Anticoagulation & Fibrinolysis
Used in:
- Fibrinolytic therapy
- Thrombolysis monitoring
- Sepsis-related coagulopathy
4. Therapy Guidance
Fibrinogen levels guide:
- Cryoprecipitate
- Fibrinogen concentrate (e.g., RiaSTAP)
- ROTEM/TEG clot firmness assessment
5. Pregnancy Assessment
Low fibrinogen suggests:
- Placental abruption
- Severe postpartum hemorrhage risk
Analytical Notes
- Citrated plasma required
- Clauss assay = gold standard
- Immunologic assays measure antigen, not function
- Heparin therapy may affect results
- Fibrin degradation products (FDPs) and high D-dimer lower functional fibrinogen
Clinical Pearls
- In DIC: fibrinogen decreases, D-dimer increases, platelets fall.
- Fibrinogen is one of the last factors to fall in liver failure.
- Cryoprecipitate is the fastest way to correct low fibrinogen.
- High fibrinogen often means inflammation, not hypercoagulation alone.
- Fibrinogen >6 g/L in pregnancy is common and not pathological.
Interesting Fact
Fibrinogen is one of the largest plasma proteins, with a molecular mass of 340 kDa, and is essential for clot firmness in viscoelastic testing (TEG & ROTEM).
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Coagulation.
- ISTH (International Society on Thrombosis and Haemostasis) Guidelines.
- ASCP Coagulation Standards.
- Mayo Clinic Laboratories - Fibrinogen.
- ARUP Consult - Coagulation Studies.
- WHO Coagulation Factor I Reference Standards.
- MedlinePlus / NIH - Fibrinogen Test.