Prothrombin index, norm and value

The prothrombin index, whose norm is 95-105%, is one of the indicators characterizing the blood coagulation system. Blood coagulation is a very complex process, involving a whole cascade of special proteins called coagulation factors. Activation of this process is possible on two paths - internal and external.

It is the prothrombin index that characterizes the activation of clotting along the external pathway. It consists in the following: when tissue integrity is violated (wounded), so-called tissue thromboplastin, a special protein contained in all tissues of the body, is secreted. It triggers a cascade reaction into which other clotting factors (V, VII, and X, II, I) enter, sequentially activating each other. Eventually, a blood clot forms, and the bleeding stops.

What is said prothrombin index

Clotting factors are formed in the liver. Of these, II, V, X are vitamin K dependent. With a deficiency of this vitamin their synthesis is disrupted. Accordingly, there are violations of hemostasis. Knowing prothrombin index, the norm of which is known, the doctor can:

1. Estimate roughly the activity of II, V, also VII and X coagulating factors
2. By the value of this indicator to judge the function of the liver
3. On the saturation of the body with vitamin K
4. About the general condition of the blood coagulation system
5. This indicator can monitor the effectiveness of therapy with anticoagulants.

How is prothrombin index determined?

The prothrombin index in capillary or in venous blood is determined. In the second case, the blood on an empty stomach is taken into a test tube with an anticoagulant in a ratio of 9: 1. As an anticoagulant, sodium citrate is used. In the laboratory, the blood is centrifuged. The resulting plasma is used in the determination of prothrombin time (PT). The norm of PV is in the range of 12 to 20 seconds, depending on the activity of thromboplastin, which is used during the reaction in this laboratory.

Knowing PV of the patient, it is possible to calculate PI, that is, the prothrombin index, the norm of which in different laboratories may also be slightly different. It is equal to the ratio of the PV of a healthy person to the patient's IV, multiplied by 100:

PI = PV zdor./Pv is sick. X 100 (95-105% rate)

Clinical significance of PI

When the clotting increases, PV, or prothrombin, whose norm is from 12 to 20 seconds, is shortened, and the PI increases. It can be during pregnancy, with massive trauma, when a lot of tissue thromboplastin enters the bloodstream.

On the contrary, PV increases, and PI decreases with decreasing coagulation, for example, in case of congenital insufficiency of coagulation factors, in severe liver diseases, with vitamin K deficiency (it can occur with cholestasis, dysbacteriosis, intestinal dysfunction). Reduced PI with low fibrinogen or its functional inferiority, with the syndrome of ICE, in the presence of substances that inhibit coagulation.

What is INR

Treatment with indirect anticoagulants naturally decreases the prothrombin index. Its norm can be different in each laboratory. Therefore, in order to be able to compare the results of analyzes obtained in different laboratories, a standardized test was introduced, such as MNO. This is the calculated figure. It is determined on the basis of the ratio of the prothrombin time of the patient, normal PV value and the degree of the thromboplastin sensitivity index (MIC).

MNO = (MF b-th / MF norm) to the degree of MIC

In a healthy person, INR is in the range of 0, 8-1.2.

This indicator is used to control the effectiveness of anticoagulants. In the treatment of anticoagulants, when coagulation is reduced, (for example, after heart surgery), INR should be increased to 2-3. With increasing clotting, the INR decreases. The ratio between PI and INR is such that when the PI decreases, the MNO index increases.