6,502
edits
Changes
Jump to navigation
Jump to search
→Proteins Induced by Vitamin K Antagonism Test
Factors II, VII, IX and X are produced in the liver as non-functional precursors which become activated by carboxylation of their glutamic acid residues in the presence of vitamin K. The inactive precursors are absent from the circulation of normal animals, as they are stored in the microsomal system of the liver. However, the absence of vitamin K results in an increase in these precursors, which spill into the circulation and become known as Proteins Induced by Vitamin K Antagonism (PIVKA). Concurrently, the levels of active factors II, VII, IX and X are depleted.
Factors II, VII, IX and X are produced in the liver as non-functional precursors which become activated by carboxylation of their glutamic acid residues in the presence of vitamin K. The inactive precursors are absent from the circulation of normal animals, as they are stored in the microsomal system of the liver. However, the absence of vitamin K results in an increase in these precursors, which spill into the circulation and become known as Proteins Induced by Vitamin K Antagonism (PIVKA). Concurrently, the levels of active factors II, VII, IX and X are depleted.
The PIVKA test is modified version of PT that is designed to be more sensitive than PT for abnormalities in the vitamin-K dependent clotting factors. Diluted plasma is used to give longer clotting times, and a test-specific reagent is added. The PIVKA test is reported to be sensitive to both increases in PIVKAs and decreases in the functional coagulation factors II, VII, IX and X, although there is some debate as to whether PIVKAs actually inhibit the reaction. Although intended to be more sensitive than the PT for factors of interest, studies in dogs have shown that a PIVKA test offers little diagnosic advantage<sup>4</sup>. Additionally, only certain laboratories offer the test and the turnaround time is longer than PT.
The PIVKA test is modified version of PT that is designed to be more sensitive than PT for abnormalities in the vitamin-K dependent clotting factors. Diluted plasma is used to give longer clotting times, and a test-specific reagent is added. The PIVKA test is reported to be sensitive to both increases in PIVKAs and decreases in the functional coagulation factors II, VII, IX and X, although there is some debate as to whether PIVKAs actually inhibit the reaction. Although intended to be more sensitive than the PT for factors of interest, studies in dogs have shown that a PIVKA test offers little diagnostic advantage<sup>4</sup>. Additionally, only certain laboratories offer the test and the turnaround time is longer than PT.
The PIVKA test is prolonged in vitamin K deficiency. This can result from anticoagulant rodenticide toxicity or cholestatis. Some animals in disseminated intravascular coagulation also show a prolonged PIVKA test.
The PIVKA test is prolonged in vitamin K deficiency. This can result from anticoagulant rodenticide toxicity or cholestasis. Some animals in disseminated intravascular coagulation also have a prolonged PIVKA test.
==Tests Evaluating Fibrinolysis==
==Tests Evaluating Fibrinolysis==