The 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. In various conditions, an analysis of PTI is prescribed. The norm in healthy people is 95-105%.
Blood coagulation is carried out in two directions - the internal and external paths. The value of PTI reflects precisely the external coagulation path.
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, prothrombin protein is the second blood coagulation factor. It is synthesized with the participation of vitamin K in the liver.
The prothrombin index (Quick) allows you to determine the activity of prothrombin. This test is calculated as a percentage of the patient's blood plasma with a control sample. To monitor the functioning of the coagulation system, a blood test for PTI is prescribed. The norm in different laboratories may vary slightly, but these differences are not significant. They depend on the reagents the lab works with. In some conditions, for example, with varicose veins, heart attacks or after heart operations, the doctor sets the standards for patients, because in these cases, it is necessary to achieve hypocoagulation of the blood (reducing its coagulability). This is done to prevent thrombosis.
Who is assigned an IPT test?
Typically, in an IPT study, the norm in women is the same as in 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 biochemical blood test prescribed for PTI? The norm of this study, for example, when taking indirect anticoagulants, may be half as low. Patients taking these drugs should regularly monitor IPT and INR. A study on IPT must be carried out in the following situations:
- Before any operations.
- People taking medications have anticoagulants to prevent blood clots.
- Women during pregnancy.
- People suffering from coagulation diseases, for example, with varicose veins.
- With autoimmune disorders.
- With atherosclerosis and heart disease.
- With liver pathologies, for example, cirrhosis.
- With a deficiency of vitamin K.
- With antiphospholipid syndrome.
- For screening testing of a coagulation system.
During pregnancy, they must be tested for PTI. The norm in women during pregnancy is slightly higher than in other healthy people. This is due to a change in the hormonal background and the appearance of an additional uteroplacental circle of blood circulation.
PTI during pregnancy: normal
During pregnancy, all women must be assigned a coagulogram study. It includes:
- PTI (prothrombin index).
- INR (international normalized ratio).
- APTT (activated partial thromboplastin time).
- Fibrinogen.
All of these options are extremely important. Thus, an increase in IPT in the late stages of pregnancy to 150% and higher 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 an analysis of PTI. The norm of this indicator during pregnancy varies from 90 to 120%.
What is the increase in PTI?
So, we found that when blood thickens, the value of IPT increases. The norm of this indicator in healthy people ranges from 95 to 105%. An increase in the prothrombin index may indicate a risk of developing diseases such as:
- Myocardial infarction.
- Thromboembolism.
- Polycythemia.
- Oncological diseases.
- Detachment of the placenta in pregnant women.
What does low IPT mean?
In cases of taking anticoagulants, the level of IPI can drop to 45-40%. If there is a risk of blood clots, the doctor controls the dose of these drugs. After increasing or decreasing the dose of the drug, an analysis for PTI is required. The norm for such patients is determined by the attending physician. If the prothrombin index does not decrease when taking anticoagulants, this may indicate, for example, vitamin K deficiency, serious diseases of the liver or gastrointestinal tract as a whole, 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 coagulation factors. Such proteins are produced in the liver with the participation of vitamin K. These coagulation factors respond to the use of drugs - indirect anticoagulants, for example, Dabigatran, Warfarin or their analogues. In this case, hypocoagulation occurs, i.e. blood coagulation is much slower. For some patients, this is vital, many of them are forced to take anticoagulants for life.
PTI blood test. INR: norm
In the coagulogram, in addition to the analysis of PTI, other indicators are of great importance. With the appointment of indirect anticoagulants to patients, the IPT is reduced. But for the analysis of PTI, the norm in each laboratory may differ slightly, therefore a standardized test was introduced - INR. Doctors use it to control the blood coagulation system when patients receive anticoagulants. Thus, INR in these cases is prescribed in parallel with such an indicator as a blood test for IPT. The norm of INR in healthy people is from 0.8 to 1.2. When taking anticoagulants, coagulability 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 index decreases.
Hypocoagulation. In what situations is it needed?
In the analysis of PTI, the norm is from 95 to 100%, and the INR from 0.8 to 1.2. Recall that such standards should be absolutely healthy people. But there are situations when the INR values are vital to maintain at high numbers, respectively, the PTI indicators will be below normal, 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 who are constantly taking such medicines should regularly take a blood test for INR.
- In the case of atrial fibrillation, INR values need to be maintained within 2.0-3.0.
- Severe condition - pulmonary embolism (pulmonary embolism) - also requires maintaining the INR level in the range of 2.0-3.0.
- After heart surgery, it is necessary to take anticoagulants, while in the case of aortic valve replacement, the INR numbers need to be maintained within the appropriate range of 2.0-3.0, and with mitral valve replacement , it should be kept at 2.5-3.5.
- With some defects of the heart valves (mitral or aortic defect) and the prevention of thromboembolism, the level of this indicator should be in the range 2.0-3.0.
- In the treatment of venous thrombosis, the INR numbers should correspond to 2.0-3.0.
With a decrease in INR below acceptable limits, increase the dose of Warfarin or its analogues. This is done exclusively under the supervision of a physician and laboratory tests. But an increase in hypocoagulation (an increase in INR values) above the acceptable corridor can also negatively affect the health of patients. It is dangerous primarily by various bleeding. They can be both internal (uterine, gastric or intracavitary), and external, arising from various injuries or cuts. If the INR numbers are above the permissible limit indicated for a particular condition, then the dose of anticoagulants must be reduced. Some patients are forced to control INR levels for life.
How to take a blood test for INR and PTI?
Blood for such studies is donated in the treatment room. Venous blood is taken into a test tube with an anticoagulant, usually sodium citrate. The ratio between blood taken and anticoagulant should be 9: 1. The sample taken is mixed well by inverting the tube to prevent clot formation. Blood is immediately sent to the laboratory. The analysis must be done 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.