Prothrombin index (PTI) is one of the most important laboratory tests that characterizes the state of the coagulation system. It is expressed as a percentage. Under various conditions, an analysis for PTI is prescribed. The norm in he althy people is 95-105%.
Blood coagulation is carried out in two directions - internal and external ways. The PTI value reflects exactly the extrinsic clotting pathway.
What is prothrombin?
The formation of blood clots and blood clots occurs under the influence of a special protein - thrombin, which, under the influence of some biochemical processes, is converted from prothrombin. Thus, the prothrombin protein is the second blood coagulation factor. It is synthesized with the participation of vitamin K in the liver.
Prothrombin index (according to Quick) allows you to determine the activity of prothrombin. This test is calculated as a percentage of the patient's blood plasma values with a control sample. To control the work of the coagulation system, a blood test for PTI is prescribed. norm in variouslaboratories may differ slightly, but these differences are not significant. They depend on the reagents with which the laboratory works. In some conditions, for example, with varicose veins, heart attacks, or after heart surgery, the doctor sets the norms for patients, because. in these cases, it is necessary to achieve blood hypocoagulation (decrease in its coagulability). This is done to prevent blood clots.
Who is assigned an IPT test?
Usually, in the study of PTI, the norm for women is the same as for men. This indicator changes only during pregnancy, and there are a number of reasons for this, which we will talk about a little later. In what cases is a PTI biochemical blood test prescribed? The norm of this study, for example, when taking indirect anticoagulants, can be two times lower. Patients taking such drugs should regularly monitor IPT and INR. Research on PTI is mandatory in the following situations:
- Before any operations.
- People taking anticoagulant medications to prevent blood clots.
- Women during pregnancy.
- People suffering from diseases of the coagulation system, such as varicose veins.
- For autoimmune disorders.
- With atherosclerosis and heart disease.
- With liver pathologies, for example, cirrhosis.
- For vitamin K deficiency.
- With antiphospholipid syndrome.
- For screening testing of the coagulation system.
During the periodpregnancy must be tested for PTI. The norm in women during pregnancy is slightly higher than in other he althy people. This is due to a change in the hormonal background and the appearance of an additional uteroplacental circulation.
PTI during pregnancy: the norm
During pregnancy, all women are required to undergo a coagulogram study. Includes:
- PTI (prothrombin index).
- INR (International Normalized Ratio).
- APTT (activated partial thromboplastin time).
- Fibrinogen.
All these parameters are extremely important. Thus, an increase in PTI in the last stages of pregnancy to 150% or more may indicate a risk of placental abruption. And with a decrease in this indicator before childbirth below 80%, there is a risk of bleeding during childbirth or in the postpartum period. Thus, it is especially important to examine the coagulation system at the end of pregnancy. To do this, pass the analysis of PTI. The rate of this indicator during pregnancy varies from 90 to 120%.
What does the increase in PTI indicate?
So, we found out that when the blood thickens, the value of PTI increases. The norm of this indicator in he althy people ranges from 95 to 105%. An increase in the prothrombin index may indicate the risk of developing diseases such as:
- Myocardial infarction.
- Thromboembolism.
- Polycythemia.
- Oncological diseases.
- Detachmentplacenta in pregnant women.
What does a low IPT mean?
In cases of taking anticoagulants, the level of IPT can drop to 45-40%. With the threat of blood clots, the dose of these drugs is controlled by a doctor. After increasing or decreasing the dose of the drug, an analysis for PTI is mandatory. The rate for such patients is determined by the attending physician. If the prothrombin index has decreased not while taking anticoagulants, then this may indicate, for example, vitamin K deficiency, serious diseases of the liver or gastrointestinal tract in general, and in pregnant women before childbirth, the risk of bleeding during labor.
What is INR?
This indicator is the standard for determining blood coagulation. The INR value responds to the activity of certain blood proteins, which are clotting factors. Such proteins are produced in the liver with the participation of vitamin K. These coagulation factors respond to the intake of drugs - indirect anticoagulants, for example, "Dabigatran", "Warfarin" or their analogues. In this case, hypocoagulation occurs, i.e. blood clotting is much slower. For some patients, this is vital, many of them are forced to take anticoagulants for life.
PTI blood test. INR: normal
In the coagulogram, in addition to the PTI analysis, other indicators are of great importance. When patients are prescribed indirect anticoagulants, PTI decreases. But for PTI analysis, the norm in each laboratorymay differ slightly, so a standardized test was introduced - INR. Doctors use it to control the blood coagulation system when patients take anticoagulants. Thus, in these cases, the INR is prescribed in parallel with such an indicator as a blood test for PTI. The norm of INR in he althy people is from 0.8 to 1.2. When taking anticoagulants, clotting decreases, hypocoagulation occurs, and INR can increase 2-3 times the norm, for example, during heart surgery or varicose veins to prevent blood clots. If the blood becomes thicker, its coagulability increases and, accordingly, the INR decreases.
Hypocoagulation. In what situations is it needed?
In the analysis of PTI, the norm is from 95 to 100%, and the INR is from 0.8 to 1.2. Recall that absolutely he althy people should have such norms. But there are situations when it is vital to maintain the INR values at high numbers, respectively, the PTI indicators will be below the norm, i.e. this will be the state of hypocoagulation. This condition is achieved by taking indirect anticoagulants. The dose of the drug can only be determined by a doctor. Patients taking these drugs on a regular basis should have regular INR blood tests.
- In case of atrial fibrillation, INR values should be maintained within 2, 0-3, 0.
- Severe condition - PE (pulmonary embolism) - also requires maintaining the INR level within 2, 0-3, 0.
- After surgery onthe heart requires anticoagulants, while in the case of aortic valve replacement, the INR numbers must be maintained within the appropriate range of 2.0-3.0, and in case of mitral valve replacement - at the level of 2.5-3.5.
- For some heart valve defects (mitral or aortic disease) and prevention of thromboembolism, the level of this indicator should be within 2, 0-3, 0.
- In the treatment of venous thrombosis, the INR numbers should correspond to 2, 0-3, 0.
When INR values decrease below acceptable limits, the dose of "Warfarin" or its analogues is increased. This is done exclusively under the supervision of a doctor and laboratory tests. But an increase in hypocoagulation (an increase in INR values) above the acceptable corridor can also adversely affect the he alth of patients. This is dangerous in the first place with various bleeding. They can be both internal (uterine, gastric or intracavitary), and external, resulting from various injuries or cuts. If the INR figures are above the acceptable limit indicated for a particular condition, then the dose of anticoagulants must be reduced. Some patients have to monitor INR levels for life.
How to take a blood test for INR and PTI?
Blood for such studies is taken in the treatment room. Venous blood is taken into a test tube with an anticoagulant, which is usually sodium citrate. The ratio between the collected blood and anticoagulant should be 9:1. The sample taken is mixed well.by inverting the tube to prevent clot formation. The blood is immediately sent to the laboratory. The analysis must be carried out no later than two hours after blood sampling. Failure to comply with these conditions may distort the result of the analysis. Blood is usually donated in the morning on an empty stomach, but if necessary, this analysis can be done at other times by cito, i.e. urgently.
