Increasingly when requesting the vitamin K level laboratories may offer protein induced by vitamin K absence or antagonist-II (PIVKA-II). This marker increases when the vitamin K is low or inhibited e.g. by warfarin. There are three different subtypes of vitamin K and PIVKA-II therefore provides a sensitive marker of tissue status of vitamin K activity/concentration.
Liver disease can increase PIVKA-II causing a false result.
A blood sample taken from a vein in the arm
Vitamin K is a fat soluble vitamin and is important in the synthesis of clotting factors. Therefore, a deficiency in vitamin K is often discovered when unexpected or excessive bleeding or easy bruising occurs.
The primary test used to investigate excessive bleeding is the prothrombin time (PT). If the result of the PT is prolonged and it is suspected to be due to low levels of vitamin K, then oral supplements or injections of the vitamin will be administered. If the bleeding is resolved and the PT/INR results return to normal, then vitamin K deficiency is assumed to be the cause.
Direct assessment of vitamin K status can be useful in patients with obstructive liver disease, malabsorption due to coeliac disease, or pancreatitis and in patients on long-term parenteral nutrition.
For more on this, see the article on Vitamin K Deficiency.