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Fibrinogen
Test CodeFIBR
Alias/See Also
FIB, Fibrinogen level
Preferred Specimen
4.5 mL blood (9:1 blood to anticoagulant) in 5 ml tube
Instructions
Tube must be filled to the line to ensure the proper ratio of blood to anticoagulant.
NOTE: Collection of blood for coagulation testing through intravenous lines that have been previously flushed with heparin should be avoided, if possible. If the blood must be drawn through an indwelling catheter, possible heparin contamination and specimen dilution should be considered. When obtaining specimens from indwelling lines that may contain heparin, the line should be flushed with 5 mL of saline, and the first 5 mL of blood or 6-times the line volume (dead space volume of the catheter) be drawn off and discarded before the coagulation tube is filled. For those samples collected from a normal saline lock (capped off venous port) twice the dead space volume of the catheter and extension set should be discarded.
NOTE: Collection of blood for coagulation testing through intravenous lines that have been previously flushed with heparin should be avoided, if possible. If the blood must be drawn through an indwelling catheter, possible heparin contamination and specimen dilution should be considered. When obtaining specimens from indwelling lines that may contain heparin, the line should be flushed with 5 mL of saline, and the first 5 mL of blood or 6-times the line volume (dead space volume of the catheter) be drawn off and discarded before the coagulation tube is filled. For those samples collected from a normal saline lock (capped off venous port) twice the dead space volume of the catheter and extension set should be discarded.
Transport Container
3.2% Sodium Citrate (light blue-top)
Specimen Stability
Room temperature: 4 hours, Refrigerated platelet-poor plasma: 4 hours, Frozen platelet-poor plasma: 2 weeks
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Moderate or grossly hemolyzed specimens are unacceptable.
Limitations
1. In patients receiving drugs that affect the fibrinolytic system, the plasma levels of fibrinogen degradation products (FDP) may be extremely high. FDPs may inhibit both thrombin action of fibrinogen and fibrin polymerization. At normal fibrinogen concentrations, FDPs have a minimal effect on the fibrinogen assay. At fibrinogen concentrations below 150 mg/dL, FDPs greater than 130 µg/mL increasingly inhibit the thrombin clotting rate assay. High levels of paraproteins may interfere with the polymerization of fibrin monomers.
2. The clinical use of topical bovine thrombin has led to the generation of antibodies in some patients. These antibodies may lead to artifactual prolongation of the thrombin clotting rate assay of fibrinogen.
3. Heparin may interfere with this assay. However, the STA®-Fibrinogen reagent contains a specific inhibitor of heparin. Any prolongation of the assay is therefore, related to a real coagulation factor deficiency of Fibrinogen.
2. The clinical use of topical bovine thrombin has led to the generation of antibodies in some patients. These antibodies may lead to artifactual prolongation of the thrombin clotting rate assay of fibrinogen.
3. Heparin may interfere with this assay. However, the STA®-Fibrinogen reagent contains a specific inhibitor of heparin. Any prolongation of the assay is therefore, related to a real coagulation factor deficiency of Fibrinogen.
Reference Range
200-400 mg/dL
Clinical Significance
An increase of fibrinogen level is found in cases of diabetics, inflammatory syndromes, obesity, and pregnancy. A decrease of the fibrinogen is observed in DIC and fibrinogenolysis. Furthermore, fibrinogen seems to be involved in the pathogenicity of the thrombotic cardiovascular events. Fibrinogen is composed of six chains: two alpha, two beta and two gamma chains. Thrombin (factor IIa) breaks up the fibrinogen molecule to split out two fibrinopeptide fragments from the Aa chain and two fibrinopeptide fragments from the Bß chain. The fibrin monomers that are produced from these reactions then aggregate to form fibrin, which is subsequently stabilized by factor XIIIa. The first step of this stabilization consists of the binding of two y chains of two fibrin monomers. This binding is the origin of the D-Dimer, the degradation product that is specific of fibrin.
