Frequently asked questions for the QuickVet® Equine Fibrinogen™ test

What is Fibrinogen?

Fibrinogen (factor I) is a soluble plasma glycoprotein, synthesized by the liver, that is converted by thrombin into fibrin during blood coagulation. This is achieved through processes in the coagulation cascade that activate the zymogen prothrombin to the serine protease thrombin, which is responsible for converting fibrinogen into fibrin. Fibrin is then cross linked by factor XIII to form a clot.

Why is Fibrinogen used diagnostically?

Fibrinogen plasma concentration normally increases within 24 to 48 hours in response to inflammation. Fibrinogen is therefore considered one of the acute-phase proteins. When measured in citrated plasma a level above the normal range of 2.0 – 4.0 g/L indicates a systemic inflammatory response. Age and breed have to be taken into consideration when evaluating the fibrinogen level (Lacerda et al. 2006). New born foals normally have 40 % less plasma fibrinogen reaching normal level 4 – 7 days after birth (Barton et al., 1995) meaning that normal fibrinogen range in newborn foals is lower compared to older foals and adult horses.

Detection of low levels of fibrinogen can indicate a systemic activation of the clotting system, with consumption of clotting factors faster than synthesis. Excessive clotting factor consumption is known as Disseminated Intravascular Coagulation (DIC). In the context of acute critical illness such as sepsis or trauma DIC can be difficult to diagnose, but a strong clue is detection of low fibrinogen and concomitant observation of prolonged clotting time (PT and
aPTT). Liver problems can also result in decreased levels of fibrinogen.

Has there been any scientific results reported on fibrinogen as a useful diagnostic marker?

The usefulness of fibrinogen as a marker of inflammation, trauma and various types of infections have been reported in a number of scientific papers

General inflammatory response due to an infection. Fibrinogen normally increases within 24 to 48 hours from a normal level of 2-4 g/L and may exceed 10 g/l on day 4 - 7 post infection. It is not uncommon in horses to have increased plasma fibrinogen levels as the sole indicator of inflammation.
S. Jacobsen et al. 2009, S. Jacobsen 2007, Pusterla et al. 2006, Allen & Kold 1988.
Surgical trauma. Levels of serum amyloid A, fibrinogen and iron reflects the intensity of the surgical trauma, where as WBC do not do this. Fibrinogen is therefore a good diagnostic marker to monitor the healing process after a surgical procedure.
S. Jacobsen et al. 2009, Allen & Kold 1988, Feige K. et al. 2003.
Bacterial infection. The fibrinogen level can be used to predict the time course of an bacterial infection as has been shown with Escherichia coli endotoxin. It has also been shown to be an effective screening tool to diagnose Rhodococcus Equi infections in foals. Fibrinogen concentrations has also been shown to enable a more precise diagnosis of the severity of an inflammation than that based simply on clinical conditions in respiratory diseases, particularly bacterial pneumonia.
Burrowes 1981, Heidmann et al. 2006, Takizawa % Hobo 2006.
Viral infection. Horses with equine influenza and herpes virus 2 has been proven to show elevated fibrinogen levels 3 days post infection.
Heidmann et al. 2006, Sutton et al. 1997 / 98, Hubert et al. 2004.
Parasite infection. Parasitized (Strongelus Vulgaris) ponies showed in a study to have significantly elevated fibrinogen levels compared to a control group 9, 14, 21 and 45 days after infection.
Heidmann et al. 2006, Sutton et al. 1997 / 98, Hubert et al. 2004.
Aseptic arthritis. Experimentally induced aseptically inflammation showed a significant increase in fibrinogen with a maximum level 3 - 6 days post-injections.
Hubert et al. 2004, Hulten et al. 2002.

Does the method of blood sample collection matter?

Proper technique for blood collection is essential for accurate results. Blood should be drawn as a-traumatically as possible in a syringe or sodium citrate tube. Samples with visible clotting or debris should be discarded and a fresh sample obtained. The sample should be prepared and tested within 12 hours.

When would clinics use the Equine Fibrinogen™ test?

The QuickVet® Equine Fibrinogen™ test should be used to confirm suspicion of an inflammatory condition in the patient and to monitor disease progression. The test can with benefit be used before other clinical signs is present.

Clinics use the test for:

Determination and monitoring of a systemic inflammation
Monitoring of surgical trauma and the healing process
Tool to aid in the diagnosis of bacterial, viral and parasite infections
Monitoring therapy and disease progression

Does the QuickVet® Equine Fibrinogen™ test have normal reference intervals?

Yes, the test package insert provides normal reference values. For Equine the normality range is 1.5 g/L - 4.0 g/L. These reference ranges has been based on an extensive analysis of fibrinogen normality ranges reported in scientific literature. The normality range is displayed on the screen together with the result and on printouts.

What animals can be tested with the QuickVet® Equine Fibrinogen™ test?

While the QuickVet® Equine Fibrinogen™ test will work with most species, it has only been validated for Equine.