Background and Diagnostic Use

This test is used for determination of fibrinogen concentration as an indicator of inflammation in large animals. Fibrinogen is an acute phase reactant protein and will increase within 24 to 48 hours in response to inflammation. Increased values are also seen in cows with renal disease. The test is based on the difference in refractometer protein values before and after precipitation of fibrinogen by heat.. This is a crude estimate of fibrinogen concentration (values also only increase in increments of 100 mg/dL) and is insensitive to low fibrinogen concentrations with hemostatic defects, e.g. disseminated intravascular coagulation (i.e. it should not be used as a test to detect hypofibrinogenemia). The method is as follows:

Sample

EDTA-anticoagulated blood only (purple top tube)

Method

Two microhematocrit tubes are filled with EDTA-anticoagulated blood. One is centrifuged and the total protein in the plasma is measured by refractometer. The second tube is heated at 56°C for 3 minutes, which precipitates the fibrinogen. The second tube is then centrifuged and the protein result read similarly. The protein result in the heated tube is subtracted from the result in the unheated tube; the difference is equivalent to the fibrinogen that was removed from the plasma in the second tube by heating and centrifuging.

Interferences

Lipemia and hemolysis may interfere with the refractometer protein measurement, invalidating the results.