Summary
In vitamin K deficiency (either absolute or induced by oral anticoagulants) two types
of prothrombin occur. One is not distinguishable from normal prothrombin. It generates
thrombin quickly in a medium in which the factors V, VII and X, thromboplastin and
Ca++ are present in sufficient amounts. The other is converted into thrombin much more
slowly under the same conditions. In the onestage prothrombin assay only the first
form is measured, in a two-stage prothrombin assay both forms are estimated. This
accounts for the well-known discrepancy between these two tests in vitamin K deficiency.
The abnormal prothrombin can be considered one of the Proteins Induced by Vitamin
K Absence. The occurrence of this kind of proteins fits in the concept of the action
of vitamin K as a co-factor in a system that converts polypeptide-precursors into
coagulation factors.
