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Coagulation
Fibrinogen
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Fibrinogen (factor I) is the precursor of fibrin and also an acute-phase protein. Its level reflects both clotting capacity and inflammatory state.
Reference interval
| Conventional (mg/dL) | SI (g/L) | |
|---|---|---|
| Adults | 200–400 mg/dL | 2–4 g/L |
Specimen: Citrated plasma · Conventional × 0.01 = SI
Causes of high values
Acute-phase response (infection, inflammation, malignancy, tissue injury), pregnancy, oestrogens, smoking, obesity and nephrotic syndrome.
Causes of low values
DIC, severe liver disease, massive haemorrhage, fibrinolytic therapy, asparaginase, and congenital afibrinogenaemia or dysfibrinogenaemia. Levels below about 100-150 mg/dL (1.0-1.5 g/L) are clinically relevant in bleeding.
Pre-analytical and method notes
The Clauss functional method is standard; derived (PT-based) estimates are less accurate. Reference intervals vary by method and laboratory (commonly 200-400 mg/dL, 2-4 g/L); levels are raised in pregnancy and acute illness, so a normal value in DIC can be misleading. Heparin and very high D-dimer or fibrin degradation products may interfere.
References
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. Elsevier — Tier 3 (textbook)
- Loscalzo J, et al.. Harrison's Principles of Internal Medicine. McGraw-Hill, 21st edition (2022) — Tier 3 (textbook)
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