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Test ID: Antigen-Fibrinogen
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Fibrinogen Antigen
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Immunoturbidimetric assay
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Method name and description
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Immunoturbidimetric method, based on antigen-antibody reaction: fibrinogen antigen of the sample reacts with polyclonal rabbit anti-human fibrinogen antibodies, leading to latex particles agglutination. This agglutination can be directly detected by a change of absorbance. The absorbance change is directly proportional to the amount of fibrinogen in the sample.
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Clinical information
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Fibrinogen (clotting factor I) is an essential protein responsible for blood clot formation. In the final step of the coagulation cascade, thrombin converts soluble fibrinogen into insoluble fibrin strands that crosslink and form a clot.
Fibrinogen is synthesized in the liver and has a biological half-life of 3 to 5 days in the circulating plasma. Fibrinogen deficiencies can be congenital or acquired and lead to prolonged coagulation times. Isolated fibrinogen deficiency is an extremely rare inherited coagulation disorder.
Acquired fibrinogen deficiency is most commonly caused by, acute or decompensated intravascular coagulation and fibrinolysis. Other causes of fibrinogen deficiency include advanced liver disease, L-asparaginase therapy, or fibrinolytic agents (eg, streptokinase, urokinase, tissue plasminogen activator).
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Specimen type / Specimen volume / Specimen container
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Sodium Citrated whole blood tube.
Specimen Volume: 2.7ml
Container/Tube: Light-blue top (citrate)
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Collection instructions / Special Precautions / Timing of collection
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1. Samples collected in HMC facilities MUST reach the coagulation laboratory within 1 hour of collection.
2. Samples collected in non-HMC facilities / external clients: MUST reach coagulation laboratory within 1 hour of collection, if not applicable, centrifuge the whole blood and carefully remove the plasma (by pipette not by decanting ) and send it in a temperature-controlled environment (18- 25 ºC) within 2 hours of centrifugation. If the transportation of the plasma can’t be within a maximum of 2 hours, prepare platelet-poor plasma as follows:
- Re-centrifuge the plasma again.
- Remove the top portion of plasma leaving approximately 250 ul in the bottom to discard.
- The double-centrifuged plasma should be aliquoted into labeled plastic tubes.
- Freeze immediately at -20 ºC or below
- Specimens must arrive frozen.
3. If patient HCT is >55%, test will not be processed .The ordering Physician will be contacted to reorder the test and call the patient to go to Phlebotomy for recollection. Instruct the patient to inform the phlebotomy about his high HCT% , the phlebotomy will contact the lab to request a coagulation tube after adjusting amount of anticoagulant.
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Relevant clinical information to be provided
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Clinical presenting, bleeding history, anticoagulants, medications and family history.
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Storage and transport instructions
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Specimen Rejection Criteria
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- Wrong anticoagulant. Sample must be collected in blue top tube containing 3.2% liquid sodium citrate.
- Clotted samples.
- Broken / leaking sample tubes.
- Under-filled or over-filled. It is critical that the tubes are adequately filled so that the ratio of blood to anticoagulant is 9:1. Under-filled tubes will yield falsely increased clotting times due to excess of anticoagulant.
- Grossly hemolyzed
- Old specimens - exceeding the stability time of 4 hours from sample collection.
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Biological reference intervals and clinical decision values
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> or =18 years : 2.12 – 3.98 g/L
Reference values have not been established for patients that are less than 18 years of age.
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Factors affecting test performance and result interpretation
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Factors
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Limits
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Hemoglobin
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1000 mg/dL
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Bilirubin (Free)
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60 mg/dL
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Bilirubin (Conjugated)
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60 mg/dL
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Intralipids
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1000 mg/dL
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Rheumatoid Factor
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3000 IU/mL
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Heparin (UFH/LMWH)
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2/2 IU/mL
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Rivaroxaban
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400 ng/mL
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Apixaban
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400 ng/mL
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Dabigatran
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400 ng/mL
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Edoxaban
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400 ng/mL
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Argatroban
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400 ng/mL
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Fibrinogen degradation products (FDP)
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130 μg/mL
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Hook effect : No significant hook effect up to 27 g/L of Fibrinogen using this method .
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Turnaround time / Days and times test performed / Specimen retention time
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Turnaround time: Stat:1 hr. Routine:4 hrs
Days and times test performed: Daily
Specimens are not stored, and so are discarded after testing.
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