Why Factor V and ALT?
Factor V
One of the liver's key functions is the synthesis of most coagulation factors. Among these factors, Factor V (FV) has unique characteristics that make it an excellent and reliable biomarker of liver function.
- Synthesised exclusively by the liver
- It is not dependent on vitamin K
- Has a short half life (12-36h)
These characteristics mean its synthesis depends solely on proper liver function and its plasma levels reflect liver function at the time of measurement.
FV as a liver biomarker
Factor V levels are currently considered for the diagnosis of acute liver failure, as one of the parameters included in the Clichy criteria.
However, it was not until 2015 that Factor V levels were studied in relation to liver transplantation, demonstrating that it is a prognostic biomarker of short-term mortality following the procedure.
Later, in 2019, Factor V was analysed as a potential marker of EAD after liver transplantation, showing that it is indeed a marker of EAD and a good predictor of graft loss post-transplantation.
ALT
Alanine transaminase is an intracellular enzymes that are released into the bloodstream in response to hepatocyte injury. For this reason, they are used not only as markers of hepatocellular dysfunction, but also as indicators of hepatocyte damage. They are therefore considered markers of hepatic cytolysis rather than of synthetic liver function. ALT is found almost exclusively in large amounts in the cytoplasm of hepatocytes, making it the most specific plasma biomarker for liver injury.
What about AST?
Aspartate aminotransferase is located both in the cytoplasm (20%) and the mitochondria (80%). Although it is found mainly in the liver and heart, it is also present in skeletal muscle, pancreas, kidneys, and brain. Therefore, elevated levels cannot be attributed exclusively to liver function. Furthermore, it may be misleading in certain situations, as it can be disproportionately elevated in some grafts—such as those from DCD donors—without necessarily indicating graft dysfunction.
Want to know more about FV?
It is a plasma cofactor synthesised in an inactive form, which, once activated by thrombin (or by factor Xa), becomes part of the prothrombinase complex. This complex catalyses, on the platelet surface, the conversion of prothrombin into large amounts of thrombin. Therefore, Factor V plays a role in thrombin activation, interacts with other coagulation factors, and regulates the coagulation cascade by acting as a cofactor in the regulation of factor VIII.