ISSN 2398-2942      

Plasma: fibrinogen

icanis
Contributor(s):

Kathleen P Freeman


Overview

  • Fibrinogen: soluble plasma protein produced in hepatic parenchymal cells and stored until required.
  • Half-life of 2.3-2.7 days makes it an acute phase indicator.
  • Inflammation (bacterial, chemical, neoplastic, traumatic) increases [fibrinogen] a temporary increase if acute and persistent if chronic inflammation.

Sampling

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Tests

Methodologies

Chemical method

  • Thrombin + plasma → fibrin clot which is washed, dried and weighed. Time consuming and may be adversely affected by large amounts of heparin.

Turbidometric method

  • Plasma + ammonium sulphate → precipitated fibrinogen → resulting turbidity measured photometrically.

Immunologic method

  • Antifibrinogen is complexed with latex particles and mixed with diluted blood. Agglutination occurs at [fibrinogen] >10 g/l.
  • Rapid, easy but not quantitative and does not differentiate fibrinogen from its breakdown products.

Thrombin time or thrombin clot time

  • Measures plasma [functional fibrinogen].

Millar method

  • EDTA + whole blood drawn into microhematocrit tube → tube sealed at one end → centrifuge for 5 minutes in microhematocrit → place in water bath at 56°C for 3 minutes. Fibrinogen is above buffy coat layer. Measure length of precipitate in relation to original column of plasma.

Heat precipitation refractometry method

  • EDTA whole blood drawn into 4 microhemocrit tubes, which are sealed and centrifuged for 5 minutes.
  • 2 tubes are used to determine plasma proteins by refractometer.
  • Remaining 2 tubes heated in heat block or water bath at 56°C for 3-5 minutes. Then recentrifugred and used for plasma protein determination by refractometer.
  • Plasma fibrinogen determined by calculation:
    • Original plasma protein (g/l) - plasma protein following heating (g/l) = fibrinogen (g/l).

Availability

  • Widely available at commercial laboratories.
  • Some practice laboratories.

Validity

Sensitivity

  • Sensitive.
  • Heat precipitation method not accurate in detecting decreases in fibrinogen.

Specificity

  • Low specificity.

Predictive value

  • Best used as part of a blood profile.

Technique (intrinsic) limitations

  • Does not provide specific diagnoses.

Technician (extrinsic) limitations

  • Refractory method may be inaccurate because of interference from hemolysis or lipemia.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from VetMedResource and PubMed.
  • O'Donnell M R, Slichter S J, Weiden P L & Storb R (1981) Platelet and fibrinogen kinetics in canine tumors. Cancer Res 41(4), 1379-1383.

Other sources of information

  • Cowell R L, Tyler R D & Meinkoth J H (1999) Diagnostic Cytology and Hematology of the Dog and Cat. 2nd edn. Mosby, USA.
  • Duncan J R, Prasse K W & Mahaffy E A (1994) Veterinary Laboratory Medicine Clinical Pathology. 3rd edn. Iowa University Press, USA
  • Jain N C (1993) Essentials of Veterinary Hematology. Lea & Febiger, USA.

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