Fibrinogen (or Factor I) is of the coagulation factors and it is essential to the blood-clotting mechanism. It is part of the “common pathway” (fourth reaction) in the coagulation system. Fibrinogen is converted to fibrin by the action of thrombin during the coagulation process. Fibrinogen, which is produced by the liver, is also an acute-phase reactant protein. Fibrinogen levels increase sharply due to tissue inflammation or tissue necrosis.
High levels of fibrinogen have been associated with an increased risk for coronary heart disease (CHD), stroke, myocardial infarction (MI), and peripheral arterial disease. Reduced levels can be seen in patients with liver disease, malnourished states, and consumptive coagulopathies (e.g., disseminated intravascular coagulation [DIC]). Bank stored blood doesn’t contain fibrinogen in order to avoid any possibility of coagulation during blood transfusion procedures. When patients receive large amounts of blood, their fibrinogen levels will decrease. Reduced levels of fibrinogen will cause prolonged prothrombin (PT) and partial thromboplastin (aPTT) times.
Causes of Fibrinogen False Indications
- Blood transfusions within a month before the test may affect test results.
- Diets rich in omega-3 and omega-6 fatty acids reduce fibrinogen levels.
- Drugs that may cause increased levels include estrogens and oral contraceptives.
- Drugs that may cause decreased levels include anabolic steroids, androgens, asparaginase, phenobarbital, streptokinase, urokinase, and valproic acid.
Normal Fibrinogen Levels
Fibrinogen levels are measured in terms of milligrams per liter or grams per liter using the international system units (SI). The following are the Normal Fibrinogen Levels range for both newborns and adults:
Newborns: 125 to 300 mg/dL (or 1.25 to 3 g/L).
Adult: 200-400 mg/dL (or 2 to 4 g/L).
Causes of High Fibrinogen Levels
Pregnancy is associated with increased serum proteins (including fibrinogen). Since fibrinogen is an acute-phase reactant protein, High Fibrinogen Levels are associated with the following conditions:
- Acute inflammatory reactions (e.g., Rheumatoid Arthritis [RA], Glomerulonephritis).
- Acute Infection such as Pneumonia.
High Fibrinogen Levels are merely an observation with no known pathophysiology in the following conditions:
- Coronary heart disease (CHD).
- Peripheral Vascular Disease.
- Cigarette smoking.
Causes of Low Fibrinogen Levels
- When Fibrinogen is not made in adequate volume this leads to Low Fibrinogen Levels. Low production of Fibrinogen can be an indication of Liver Disease either hepatitis or cirrhosis.
- Primary and secondary fibrinolysins act to destroy fibrinogen within the serum which lowers Fibrinogen levels. This can be a result of Fibrinolysins or Consumptive coagulopathy (e.g., Disseminated Intravascular Coagulation).
- Congenital afibrinogenemia: A genetic defect precludes the synthesis of fibrinogen.
- Severe protein depletion is associated with reduced levels of fibrinogen (a protein). Low Fibrinogen Levels due to protein depletion can be detected in patients with Advanced Carcinoma or Malnutrition.
- Large-volume blood transfusion: Fibrinogen does not exist in normal levels in banked blood. The more that is transfused, the more the native fibrinogen is diluted.