Prothrombin, prothrombin index and time: blood norms, interpretation of tests

As a rule, when applying for hospital treatment, each patient the next morning before breakfast undergoes mandatory finger prick tests ( general analysis blood, sugar and prothrombin). These laboratory tests are considered the main indicative studies, since they are the ones who “paint” the overall picture of the patient’s condition. Other (biochemical, including coagulation) tests can be prescribed on the day of admission, if the problem in the patient’s body is clearly defined, or if, in the process of examination and treatment, the goal is to thoroughly study the functional abilities of the patient’s organs and systems and monitor the effectiveness of therapy .

The unique medium moving through blood vessels, according to its characteristics, is classified as connective tissue. Being in a liquid state and having fluidity, which prevents gluing shaped elements, blood, at the same time, is able to quickly clot when the vascular wall is damaged. She has this opportunity thanks to the blood coagulation system and its factor, one of which is prothrombin . It should be noted that all factors without violating the integrity of the vascular walls are in an inactive state. Activation of factors and formation of blood clots inside circulatory system without any reason, it threatens with serious complications for the body.

What is prothrombin?

stages of blood clotting

Prothrombin or factor II (FII) of the prothrombin complex is a protein (glycoprotein), a plasma factor of the coagulation system, which belongs to alpha2-globulins and is synthesized by hepatocytes (liver cells). It's important to note that prothrombin production will become noticeably more difficult if the amount of vitamin K in the body decreases for some reason, which synthesis so needs this factor. If everything is normal in the body, then prothrombin does not show any activity, remaining as a precursor of thrombin - an enzyme that causes polymerization and the formation of a clot (thrombus), if the need arises.

In the circulating blood, plasma factors, being in the form of an inactive form of profactor (prothrombin → thrombin), always remain in relatively constant concentrations; activation occurs under the influence of coagulation factor XII ( internal system hemostasis) and when blood comes into contact with damaged tissues (external hemostasis system).

The normal level of prothrombin in the blood of healthy people is 0.10 – 0.15 g/l (1.4 – 2.1 µmol/l).

Importance of the prothrombin complex

The deficiency of this factor can be either congenital or developed during life. Congenital prothrombin deficiency is not so common, that is, it is a rare pathology. Low prothrombin from birth is caused by a mutation of recessive genes located on chromosome 11.

With hypoproteinemia of any origin, as a rule, the level of this protein is also reduced. The diseased liver (hepatocytes are the site of formation of the main factors of the prothrombin complex) and K-avitaminosis (vitamin K is involved in the synthesis of FII and other factors called K-dependent) give a sharp drop in the concentration of this indicator.

Decreased prothrombin levels cause blood to take longer to clot.. To determine how the coagulation system works depending on the level of prothrombin, in clinical practice laboratory diagnostics Coagulation tests are used, which allow one to have an idea of ​​the state of the entire prothrombin complex:

• PTI (prothrombin index, percentage);
• PO (prothrombin ratio, reciprocal PTI value, percentage);
• PTT (prothrombin time, in seconds);
• Prothrombin according to Quick (more sensitive analysis than PTI and PTV, in percentage);
• INR (international normalized ratio, percentage).

Excessive activity of prothrombin without any need is also fraught with various troubles, and sometimes even disaster for the body. Increased coagulability, the formation of clots that can close a vital blood vessel, can result in dangerous situation, even death.

Rough tests and full analysis

The study of blood coagulation, as a rule, begins with indicative methods, which make it possible to detect a coagulation abnormality (prothrombin) without revealing its essence. Then, based on the results of the analysis of blood coagulation ability, other (already specific) methods are prescribed (PTT, INR, APTT and other hemostasiogram indicators).

As for the prothrombin test, it is very important integral part and can be presented in various forms. The deficiency of prothrombin complex factors (II, V, VII, X) is determined mainly by analyzing PTT according to Quick, which primarily reveals a violation of the external formation of thromboplastin. However, it is also possible to study these indicators separately using the principle of replacement samples.

Meanwhile, we cannot ignore the indicators of blood coagulation capacity in women during planning or pregnancy, because this allows us to calculate possible risks during childbirth. Keeping in mind these indicators during pregnancy, it is possible to anticipate and prevent bleeding (if PTT is prolonged) or the development of thrombosis and premature placental abruption if the blood exhibits a particularly high tendency to clot. During the period of labor itself, the prothrombin time is somewhat shortened compared to the norm, and the prothrombin index is increased. In women during pregnancy and childbirth, the study of blood coagulation function only with prothrombin complex indicators is not enough. In order to have a complete picture functional ability hemostasis system, expectant mothers are prescribed maximum coagulogram indicators.

Prothrombin time

Prothrombin time, as a laboratory test, allows clinicians to quickly assess not only the external hemostatic system, but also the entire cascade of blood coagulation reactions.

In case of emergency situations for the body (injuries with tissue damage, heavy bleeding, necrosis and other pathological conditions), a glycoprotein, a membrane protein—tissue thromboplastin—enters the blood, which indicates the activation of the reserve (external) hemostasis system.

Tissue (cellular) thromboplastin, called tissue factor (TF), interacting with coagulation factors (FVII) circulating in the bloodstream, sequentially includes other plasma thromboplastic factors in the process. This means that the hemocoagulation system is activated and the first phase of coagulation begins - the conversion of inactive prothrombin into active thrombin. Thrombin causes the enzymatic conversion of fibrinogen into fibrin, under its influence factors (V, VIII, IX, XIII) are activated, it destroys platelets, which causes (together with Ca ++) viscous metamorphosis of blood platelets, promoting the release of platelet factors.

The norm of PTT in adults ranges from 11–15 seconds (in newborns up to 3–4 days of life – 12–18, in premature infants – 15–20). In newborn full-term infants from 4-5 days of life, the prothrombin time corresponds to that of an adult.

This indicator is increased (clotting time is prolonged) in the following pathological conditions:

1. Liver diseases, because prothrombin synthesis occurs there;
2. Lack of vitamin K, the participation of which is necessary for the synthesis of K-dependent factors (including prothrombin);
3. Increasing level blocking thrombin and other factors of the hemocoagulation system;
4. Increasing the fibrinolytic ability of blood (dissolving clots);
5. Pancreatic cancer;
6. Certain hematological pathologies (myeloid metaplasia);
7. HRD (hemorrhagic disease of the newborn);
8. High level of red blood cells in the blood (above 6.0 x 10 12 / l);

Whole blood taken with an anticoagulant (sodium citrate) is used as a biological material for studying prothrombin time using the one-stage Quick method (as the analysis is called).

PTT, Quick's test or thromboplastin time is an indicator of the external system of activation of factor II, where prothrombin time depends on the concentration of fibrinogen in the blood plasma, factors V, VII, X. The rate of PTT (Quick's test) is determined thromboplastin activity and is 12-20 seconds.

Prothrombin according to Quick

The definition of “prothrombin according to Quick” means the concentration of prothrombin complex factors as a percentage of the norm. This method currently considered one of the most in meaningful ways prothrombin studies.

The test allows you to identify the activity of factors in the prothrombin complex of the patient’s blood when compared with the known PTT of “normal” plasma. This method is undoubtedly more informative compared to calculating the PTI. Prothrombin according to Quick determines FII in a patient based on a calibration graph ( dependence of PTT on the general, total, activity of all participants in the reaction - factors of the prothrombin complex of diluted “healthy” plasma).

Normal prothrombin values ​​according to Quick vary within a wider range than PTI, and normally range from 75 to 140%. In women, the upper limits of normal are usually lower. The results of the analysis may depend on the age of the patient, the treatment he is taking (anticoagulants), and the sensitivity of the reacting substances.

Prothrombin according to Quick is primarily reduced during treatment with indirect anticoagulants(INR at the same time increases), therefore, when exercising control over anticoagulant therapy, this fact should be kept in mind first of all and, taking it into account, the patient’s blood should be analyzed in one way and in one CDL. Otherwise, you may obtain inadequate results that negatively affect the further course of anticoagulant therapy, if it is carried out at the time of the study.

Prothrombin values ​​according to Quick and PTI (prothrombin index) often give the same results in the zone normal indicators. As for the zone of low values, here the results vary noticeably, for example, you can get the following test answers: PTI - about 60%, and prothrombin according to Quick - 30%)

Prothrombin index

The prothrombin index (PTI) is the ratio between the clotting time of “healthy” plasma (control) and the clotting time of the blood of a sick person. The result is calculated as a percentage (PTT of normal plasma: PTT of patient plasma x 100%), the norm is from 90 to 105%. The inverse ratio (clotting time of the patient’s blood: clotting time of “healthy” plasma), expressed as a percentage, is called the prothrombin ratio (PR).

A low prothrombin index and prolonged PTT result in many pathological conditions:

• Congenital deficiency of certain blood clotting factors (II, V, VII, X);
• Damage to hepatocytes during chronic pathological process, localized in the liver parenchyma;
• Disseminated intravascular coagulation syndrome;
• Hemorrhagic syndrome caused by low content plasma fibrinogen (fibrinogenopenia);
• Impaired fibrinogen polymerization (dysfibrinogenemia);
• Vitamin K deficiency;
• Carrying out anticoagulant therapy;
• The use of clotting factor inhibitors, such as heparin, which inhibits the conversion of prothrombin to thrombin.

A high prothrombin index (shortened PTT) is observed in the following cases:

1. Formation of blood clots in blood vessels blocking blood flow as a result of various pathological conditions of the hemostasis system (thrombosis);
2. Consumption coagulopathies (DIC syndrome);
3. Excessive activation of the anticoagulant system, excessive formation of plasmin (hyperfibrinolysis), which leads first to bleeding, and then (with depletion of plasminogen) to thrombosis;
4. Liver diseases;
5. Increased factor VII activity ( traumatic injury tissue, necrosis);
6. Inclusion defense mechanisms in women during childbirth.

Thus, prolongation of PTT will reduce the prothrombin index and indicate a possible hypocoagulation(low blood clotting, tendency to bleed). And, conversely, a reduction in clotting time (PTT) increases the values ​​of the prothrombin index and indicates the presence of signs, that is, increased blood clotting (risk of developing thromboembolic conditions).

Unity and struggle of opposites

Disturbances in the hemostasis system lead to the development of coagulopathies, where pathology with a tendency to thrombosis is usually designated by the term, and diseases that are accompanied by increased bleeding are called " hemorrhagic diathesis" Violations of blood coagulation abilities can be hereditary in nature or result from conditions formed during life (diseases of the liver parenchyma, vitamin K deficiency, use of anticoagulants in medicinal purposes, activation of the fibrinolytic system).

The development of hemocoagulation disorder syndrome is caused by the loss (or decrease) of the ability of liver cells to biosynthesize coagulation factors. Moreover, it should be noted that the factors of the coagulation, anticoagulation and fibrinolysis systems do not exist in isolation; disruption of the activity of any one link leads to pathological conditions other components. For example:

• A disorder in the biosynthesis of the protein we are considering, prothrombin, will certainly entail a disruption in the production of other factors (VII, IX, X) and a deficiency of all components of the prothrombin complex, which will subsequently result in a decrease in the activity of FV, an increase in the concentration of fibrin monomers, a decrease in the activity of FXIII and an increase in the ability of fibrin to lysis.
• Impairment of fibrinogen metabolism will cause a change structural structure profibrin layer of blood vessels, opening the way for the movement of red blood cells through the vascular walls.

The combination of seemingly absolutely opposite properties of the above systems (provided they normal functioning) ensures the liquid state of blood, freely moving through all the blood vessels of the body, and its coagulation, if there is a need to patch a gap formed as a result of tissue damage.

Research can be expanded...

If the described methods are not fully informative, studies of the hemostatic system can be expanded, for example, by studying individual functions and quantitative values ​​of platelet and plasma factors. The prothrombin test provides a basis for searching various violations hemocoagulation, suggesting the direction of further research. For this purpose, they resort to determining other parameters of the hemostasiogram:

1. The indicator of the transition of fibrinogen to fibrin (thrombin time);

Wounds, scratches and surgical operations, which are accompanied by blood loss, would expose a person to mortal danger if the blood could not clot and form blood clots. One of these proteins that prevents huge blood loss is prothrombin. The level of prothrombin in the blood has its own indicators. Exceeding it indicates too a large number of this protein in the blood, which causes blood to thicken and can cause blood clots. Lack of prothrombin is no less life-threatening, since during the slightest bleeding a person can lose a large amount of blood. What is the established norm of prothrombin in the blood, and on what indicators this value depends, we will consider further.

Prothrombin is the protein that rolls up quickly enough, so isolate it from general composition plasma is quite difficult.

In this regard, there are several methods for determining the level of prothrombin, on which the normal indicator depends.


The prothrombin index, which is calculated as a percentage, indicates that normally in all people, regardless of age, the indicators should fall within the following limits: 95-105 %. The only exception is women during pregnancy, for whom upper limit slightly reduced to 98-100%. This process is completely natural and is dictated by the need to insure the body during childbirth, when there is a high probability of heavy blood loss.

The Quick prothrombin study, which has some differences in the detection process itself, has the following limits - 70-120. In older people, the upper limit barely reaches 110, which is also the norm and indicates age-related changes in the body caused by active aging processes. During pregnancy, especially in the third trimester, values ​​up to 110% are acceptable.

An important study that shows how long it takes for blood to clot without exposure to any anticoagulants is prothrombin time.


It is measured in seconds and for each age interval has its own norms of values:

• newborns – 14-17 s;
• children of the first year of life – 13-15 s;
• children 2-10 years old – 13-18 s;
• teenagers under 16 years old – 11-13 s;
• adults 17-45 years old – 10-15 s;
• after 45 years – 12-14 s.



During pregnancy, blood can clot quite quickly (9-12 s), which is also normal, but requires control.



Blood clotting too quickly says about its oversaturation with prothrombins, which leads to its thickening and difficulty passing through the vessels.

Ask your question to a clinical laboratory diagnostics doctor

Anna Poniaeva. Graduated from Nizhny Novgorod medical academy(2007-2014) and Residency in Clinical Laboratory Diagnostics (2014-2016).

In cases where the indicators differ greatly from the norm, there is a need to carry out additional method INR studies - international normalized ratio. This coefficient reflects the coagulation rate and also indicates possible problems with health. Normally, acceptable INR values ​​are 0.85-1.15.

In order to understand what values ​​are indicated in the analysis, you should understand what methods are used to detect prothrombin in the blood. Let's consider all technologies used in details.

What tests are used?

All methods for determining prothrombin based on the biological processes of blood coagulation which occur in several stages. At mechanical damage vessel receives a signal about the onset of bleeding. At the site of injury, thrombin factors are released, activating increased viscosity blood, resulting in the formation of a blood clot. This blood clot plugs the leak, after which the integrity of the vessel is gradually restored.

The coagulation process can have both external factors, and internal ones, the activation of which completely depends on the situation. Analysis for prothrombin can be calculated using several methods that have their own distinctive features.

The most common tests included in the coagulogram are prothrombin time, prothrombin index, and Quick prothrombin.


Prothrombin time

Prothrombin time is a numerical indicator, calculated in seconds, which shows how long it takes for blood to coagulate and transform into a blood clot. Every person has this numeric value will differ due to the characteristics of the body. To conduct the study, venous blood is required, which is transfused into a test tube with an anticoagulant (most often sodium citrate).

The vessel is placed in a centrifuge, where all blood elements, under the influence of centrifugal force, settle to the bottom and are removed. Calcium is injected into the resulting purified blood to neutralize the effect of sodium citrate in a ratio of 9:1. Next, tissue factor is added (a special reagent that acts as a catalyst for the reaction), after which the natural process coagulation.

In case there is increased content bilirubin, the analysis is carried out using a special apparatus that allows automatic counting.


Prothrombin index

This indicator is calculated using the formula, which takes the value of prothrombin time in healthy person, is divided by the indicator of the blood sample being studied, and then multiplied by 100%. The resulting value reflects the activation of blood clotting along the external pathway. This indicator helps to identify liver problems when prothrombin is produced in insufficient quantities, as well as monitor the effectiveness of anticoagulant treatment.

PTI = normal PT index/patient PT index *100%

Data to determine this indicator are taken from a previous study of prothrombin time, which used exclusively venous blood purified by centrifugation.


Prothrombin according to Quick

This research method is the most informative and reliable to date. The results obtained as a percentage reflect the activity of the prothrombin complex, which guards blood clotting. To put it simply, the resulting numerical value indicates how quickly all blood clotting mechanisms are launched.

Prothrombin in the blood is calculated according to Quick using a formula where you need to divide the indicator of temporary activity of prothrombin protein by the indicators of the control sample. The data obtained can provide a more complete picture of the state of blood clotting.

The analysis uses blood from a vein, which is cleared of red blood cells.

After this, under the influence of various catalysts and reagents, a study is carried out, the results of which are calculated using the formula.


Additional research methods

In cases where the coagulogram has conflicting indicators and there is a need for additional research, resort to such analyzes, How:

1. International normalized ratio (INR) - the test shows the relationship between the patient’s prothrombin time and the norms established for a healthy person, taking into account all the individual characteristics and conditions of the body (pregnancy, old age, the presence of chronic diseases).
2. Thrombin time - displays the indicator during which fibrinogen is transformed into fibrin.
3. Identification of platelet factors allows us to identify the quantitative composition of all components that take part in the formation of a blood clot.
4. Activated partial thromboplastin time - shows how quickly the internal processes that trigger the blood clotting mechanism are activated.



The above methods for studying prothrombin allow to identify and evaluate both the external route of hemostasis, which is determined using superficial tests, and delve into the causes of deviations, using narrower methods of studying hemostasis factors.


Indications for the study

Prothrombin study included in the coagulogram, which is a mandatory blood test during medical examination, as well as during pregnancy. This analysis may also be prescribed in the following situations:

1. There are prerequisites for development oncological diseases blood, as shown by blood tests performed earlier.
2. Liver diseases that can affect the organ’s ability to synthesize prothrombins.
3. In the presence of increased bleeding of gums, scratches and wounds, which is determined visually.
4. There is a hormonal imbalance, against the background of which the performance of the circulatory system and hematopoietic organs is reduced.
5. Autoimmune diseases that cause thickening of the blood and an increase in the number of platelets.
6. Organ diseases digestive tract, in which there is a lack of vitamin K, necessary for the synthesis of prothrombin by liver cells.
Also, using this analysis you can monitor the effectiveness of treatment for certain diseases, provoked by increased bleeding and a decrease in the number of platelets.


What can affect the result?

Since the quantitative and qualitative composition may change throughout the day, to obtain the most reliable results It is recommended to donate blood in the first hours after waking up. At this time everything is vital important functions are just beginning to be activated, so the percentage of error caused by the influence of third-party factors is reduced.

It is important that blood sampling is carried out on an empty stomach, since at the time of digestion and assimilation of food, a large amount of nutrients enters the blood, which can affect the rate of blood coagulation. It is necessary to establish a diet 2-3 days before donating blood, excluding fried and fatty foods, as well as sweets.

Alcohol and any alcoholic beverages should be avoided 4-5 days before donating blood.


Smoking, if it has become a habit, should be stopped 12 hours before the test, since high concentrations of nicotine and tar in the blood can affect the indicators, giving incorrect results.

If a person is forced to take any medications on an ongoing basis, this is reported to the doctor, who gives a referral for examination. An appropriate note is made on the control sheet, which will allow the real picture of the state of blood coagulation to be assessed, taking into account the error.

A few days before the analysis, it is recommended to exclude any physical exercise, which provoke physical fatigue. A person should have a good rest and sleep, and not experience emotional shock or stress.

If the results obtained are below normal or above normal, and the blood clotting time has its deviations, it is recommended to retake the blood a few days later in another laboratory.

Can't be underestimated human factor and features of the laboratory.


Decoding

After the blood test has been performed, the patient is given a transcript containing all the data on the state of blood clotting. It is usually presented in the form of a table divided into several columns. The first column indicates the research methodology and indicator, and the second column indicates the numerical value. The third column contains norm indicators for various groups patients, which makes it easier for people without medical education to perceive the results.

With the transcript received, you must contact the doctor who gave the referral.

He will evaluate the results obtained and decide whether additional studies are needed, or whether the coagulogram data will be sufficient to make a diagnosis.


What values ​​are considered low?

Low prothrombin index values ​​are extremely life-threatening, as they indicate slow blood clotting. This, in turn, is fraught with the development of bleeding, which in a healthy person occurs without consequences or threat to life. Indicators that tend to 80% are considered low. The lower this indicator, the more dangerous condition human health.

Some transcripts contain another column where the reasons for deviations from the norm are indicated. Low readings may be caused by:

• chronic or congenital vitamin K deficiency;
• liver pathologies in which the synthesis of prothrombin cells is slowed or defective;
• use medicines that help thin the blood (Aspirin);
• diseases of the digestive tract, in which the absorption of nutrients necessary for the synthesis of prothrombin cells is impossible.

External clinical manifestations and symptoms low indicators may be as follows:

• increased fatigue;
• problems with the digestive tract;
• frequent dysbacteriosis;
• stool disorder;
• pain in the right hypochondrium that occurs after eating fatty foods;
• pain in the left hypochondrium, which most often has a paroxysmal nature and depends on the food consumed.
A key indicator that helps determine low PTI values ​​is increased bleeding.


An ordinary finger cut can result in the loss of 100-150 ml of blood, and a deeper abrasion can even cause full-scale bleeding that is life-threatening.

In case low prothrombin reaches critical levels, that is, the need for hospitalization and full examination. Otherwise, the person is in mortal danger, and any awkward movement can trigger the development of internal bleeding. It is possible to increase the level of prothrombin in the blood of women and men using blood transfusions when it comes to critical situations that threaten death.

Treatment is carried out only after assessing the state of health, as well as after identifying the root cause. Blood transfusions cannot be used continuously.

This is only a necessary measure to support a person’s life in a critical situation.


What values ​​are considered elevated?

Indicators that significantly exceed the maximum are considered no less dangerous. acceptable standards. High prothrombin of 110-120% indicates the presence of a high concentration of platelets in the blood, which makes the blood thicker. This in turn makes it difficult for it to pass through the vessels, causing stagnation.

The most dangerous consequence, which can develop with prolonged high blood clotting rates, is the formation of blood clots. Dense blood clots that move along the bloodstream along with blood can settle on the walls of blood vessels, preventing the flow of blood to individual tissues and organs.

Deadly danger the fact is that a blood clot can break off at any time and, together with the general blood flow, enter the heart, where it will cause it to stop due to valve blockage.


An increase in blood viscosity can develop for several reasons:

1. Prolonged dehydration when the body does not receive enough fluid.
2. Having problems with the cardiovascular system.
3. Increased production of vitamin K and liver disease that precedes it.
4. Pathologies of the endocrine system.
5. Autoimmune diseases.
6. Presence of cancer.

Some medications can cause blood to thicken, so it is important to tell your doctor before testing.

Experienced laboratory technicians are able to determine the presence of high blood clotting rates after pricking a finger or drawing blood from a vein.


If the blood flows too slowly and you have to apply force to take it, then there is a high probability of high prothrombin index values. Special clinical manifestations this pathology does not exist and is often detected during a routine examination or during pregnancy.

It is strictly forbidden to take medications that can thin the blood on your own. Especially if there is a suspicion of progression of thrombophlebitis or thromboembolism. Medicines containing aspirin that thin the blood artificially, can provoke the detachment of a blood clot from the walls of the vessel and its free movement to the heart, which will entail inevitable death.

If the results obtained differ significantly from normal, it is necessary to re-take the test after 2-3 days. If the repeated results turn out to be identical, then it will be necessary to perform a series additional research, which can indicate the presence of a specific health problem.

Since if there is thick blood There is a high probability of blood clots; patients will definitely need to consult a phlebologist and a cardiac surgeon, who will be able to assess possible health risks. Treatment is selected taking into account the individual characteristics of each patient, after a full examination and identification of the root cause.

Self-medication is strictly prohibited, as it can cause death.


Prevention of normal levels


Since the quantitative indicator directly depends on a person’s lifestyle, the following recommendations can be considered prevention:

1. Normalization of nutrition and limitation of consumption harmful products, which have an increased effect on the pancreas and liver.
2. Refusal bad habits and alcohol addiction.
3. Active lifestyle with dosed physical activity.

In order to promptly identify the presence of pathologies in the body, it is worth paying attention to how quickly the blood clots when a cut occurs.

If the blood is quite difficult to stop, then you need to take the appropriate test and establish the cause of what is happening.


It is strictly forbidden to take any medications that can change blood viscosity. Only a doctor has the right to prescribe this type of treatment based on the results of the study.

Thus, prothrombin, the norm of which depends on the research method, shows the ability of blood to coagulate and form blood clots. This property is extremely important, as it provides protection during operations or injuries accompanied by a violation of the integrity of parts of the body.

Prothrombin is found in blood plasma and has a decisive influence in the process of blood clotting (another name is coagulation). Therefore, deviations of prothrombin from the norm cause increased bleeding or, conversely, indicate a risk of thrombosis. It is very important for doctors to know about this possibility if surgery is necessary, as well as when prescribing medications that affect blood clotting. Doctors also use this indicator to judge the state of the liver and gastrointestinal tract.

Prothrombin is a complex glycoprotein molecule. The decoding of this term is simple - glucose plus protein, in other words: a complex that combines carbohydrates and proteins. Prothrombin is a component that is activated at one of the initial stages after damage to body tissues that caused bleeding. The stages of blood clotting are as follows:

1. After vascular damage, platelets are activated, which adhere to the damaged tissues, stick together, forming a platelet plug.
2. At the same time, platelets begin to secrete substances that make the plug more dense.
3. At the same time, prothrombin is activated.
4. Thrombin is formed from prothrombin, which is synthesized under the action of a specific enzyme called prothrombinase.
5. Thrombin then produces fibrin from fibrinogen.
6. Fibrin, together with platelets contained in the blood, forms a blood clot.

Based on this, it is obvious that prothrombin deficiency increases bleeding time. The lack of this component is caused mainly by a deficiency of vitamin K, which plays an important role in the process of prothrombin synthesis by liver cells. Vitamin K deficiency can be caused by various circumstances, and is often accompanied by impaired bile production, which signals problems in the liver. Among the main causes of vitamin K deficiency is impaired absorption or impaired synthesis by intestinal microflora.

It is worth noting that the lack of prothrombin can be explained by other reasons. For example, substances that counteract blood clotting, treatment with indirect anticoagulants, insufficient bile supply.

How the analysis is carried out

If we talk about such a thing as prothrombin time (PTT), then you should know that this is the name of a blood test that measures the time it takes for plasma (the liquid part of the blood) to coagulate, that is, to coagulate or thicken.

Prothrombin time is measured to measure the blood's ability to form clots. Knowledge about it has a direct bearing on the dosage of anticoagulants, the degree of liver damage and the amount of vitamin K in the body.

The essence of the analysis is as follows: if damaged blood vessel The body activates the blood clotting mechanism, which stops bleeding. The coagulation process involves special proteins called coagulation factors, whose task is to promote coagulation. The PTT test accurately measures the ability of these substances to affect blood clotting.



A blood test for PTT is carried out like a regular blood test: the material is collected in a flask and analyzed. The technician then adds various chemicals to the blood sample. The time that passes from the start of adding reagents to the thickening of the blood is called prothrombin time.

The American biochemist Armand James Quick is related to the existence of this type of research. At the beginning of the last century, Quick studied the biochemistry of processes in the liver, in particular, what effect vitamin K and anticoagulants have on its work. As a result, he determined the norms of hemostasis (the process of stopping bleeding). In 1935, Quick published the prothrombin time (PTT) technique that later bore his name (the test is now known as the Quick test).

Features of the analysis

The interpretation of the prothrombin test largely depends on the laboratory in which it was performed. prothrombin test. Prothrombin time is usually related to the international normalized ratio (INR), which is 0.8-1.2. INR is calculated as the ratio of direct proportionality of the prothrombin time obtained in the test to the normal prothrombin time in a healthy person (INR = PTT test / PTT norms).

For men and women, the prothrombin rate is the same and ranges from 12.7 to 15.4 seconds. In pregnant women, the PTV transcript shows a faster rate of blood clotting:

• First trimester – 9.7-13.5 seconds.
• Second trimester – 9.5-13.4 seconds.
• Third trimester – 9.6-12.9 seconds.

The increase in clotting rate during pregnancy is explained by the fact that by this method the body reduces blood loss, which is always observed during childbirth. But on the other hand, this leads to the formation of blood clots in the veins of the legs and pelvis. Fortunately, statistics show that blood clots are rarely a concern during pregnancy: there are only 1-2 cases per 1000 women giving birth, which means there is no need to panic, unless, of course, the woman is at risk.



The formation of a blood clot in women during pregnancy is most likely in the following situations:

• During the first trimester of pregnancy or first three months after childbirth.
• If you have close relatives with thrombosis.
• Mutations of the prothrombin gene.
• The woman smokes or is constantly exposed to tobacco smoke.
• Age over 35 years.
• Overweight.
• Frequent trips to other cities during pregnancy.
• Expecting twins or triplets.
• Passive lifestyle.
• The previous birth was a cesarean section.

The appearance of blood clots in the veins during pregnancy is indicated by symptoms such as a feeling of swelling and distension in one or both legs, increased pain while walking. It may also be observed varicose veins veins in the legs (that is, they become enlarged).

The presence of such symptoms during pregnancy means that the woman must follow all the doctor’s instructions. Otherwise, complications are possible: blood thickening and a blood clot in the placenta, miscarriage, pulmonary embolism, heart attack.

Considering dire consequences, women are often interested in how to avoid blood clots during pregnancy. Doctors recommend giving Special attention healthy image life, perform the physical activity and exercises recommended for pregnant women. It is also important to comply healthy diet, and of course, be regularly examined by a doctor.

Preparing for analysis

If your doctor has prescribed a Quick test, you need to properly prepare for the test. Time between last appointment food and procedure should be more than eight hours. Before donating blood for prothrombin, you must inform the doctor about all the products, medications, herbs, and supplements that the patient uses.

This is very important because many substances thin the blood and, in fact, increase prothrombin time. The doctor will tell you which foods you need to stop eating and how long it should take after that to donate blood from a vein and get correct results. You can only drink still water in the morning.



The day before the procedure, it is necessary to limit physical activity, since it greatly affects the composition of the blood. Before donating blood, you need to rest well and be less nervous. You must not smoke for an hour before donating blood.

As a rule, the results obtained as a result of a PTV test need to be understood relatively, since they largely depend on the laboratory where they are carried out, equipment, and personnel. The doctor conducting the decoding usually takes into account the error, since the indicators may deviate from the norm under the influence various factors even if the patient has properly prepared for the analysis.

If the result shows a deviation of the PTT from the norm, you should not be alarmed right away, since this does not always indicate a disease. Perhaps the patient made a mistake and ate food from the list of non-recommended foods. For example, the day before the analysis I drank a can of beer: from drinking any alcoholic drinks You must refuse three days before the test.

Therefore, if the results are negative, the doctor prescribes a repeat test. If in this case the transcript shows a deviation from the norm, he refers the patient for further examination to determine the reasons for the too slow or rapid coagulation and appoint correct treatment.

Laboratory tests are the most important stage diagnostics of the most various diseases. Often, just blood tests are enough to find out what exactly is wrong in the body, and even to choose the right treatment. But in the vast majority of cases laboratory research used only in addition to other diagnostic procedures. And, having received the test results in their hands, patients are naturally interested in what exactly they mean. So, today we will tell you what the prothrombin index is, what is the norm for women and men, and if it is low or high, what does it mean?

“Prothrombin index” - what does it mean??

To determine the prothrombin index, blood is donated. This analysis is one of the methods for determining the functioning of the blood coagulation system. As you know, blood is a liquid. It must flow freely through the vessels in order to deliver to all corners of our body nutrients and oxygen, as well as remove metabolic products from them. In addition, the fluidity of blood allows it to perform many other vital functions.

Deviations from the norm of the prothrombin index may indicate the occurrence of a number of disorders associated with blood fluidity and its ability to clot. This indicator is usually measured as a percentage. And it is the result of dividing the time period required to clot the patient’s blood plasma by the time period required to clot the so-called control material.

What is the normal prothrombin index for men and women?

For patients of both sexes, this indicator is, in principle, practically the same. Thus, when conducting a classic biochemical study, the prothrombin index in healthy people should range from ninety-five (95) to one hundred five (105) percent.

In some life situations Slightly larger deviations are considered normal. Thus, during pregnancy, the prothrombin index in women can range from ninety (90) to one hundred and twenty (120) percent. This feature is explained by changes hormonal levels, as well as the presence in the body of a pregnant woman additional circle blood circulation

Having received tests for the prothrombin index in their hands, readers of Popular About Health can see other data in it. So, the laboratory can also determine prothrombin time. This indicator in seconds shows the period during which the patient’s blood clots. Normally in men and women it can range from nine to twelve point six seconds.

Many more laboratories record the INR value. Basically, it is calculated in patients who are being treated with indirect anticoagulants - medications designed to slow down blood clotting processes and reduce the amount of prothrombin protein. INR analysis allows you to find out how effective the therapy is. Normally, its results range from 0.85 to 1.15.

Laboratory assistants can also determine the prothrombin index in accordance with the Quick method. This study allows you to determine the degree of prothrombin activity. Its normal level ranges from seventy-eight (78) to one hundred and forty-two (142) percent.

Prothrombin index is reduced. Causes

A decrease in this indicator indicates that the patient has hypocoagulation, in other words, indicates a tendency to bleeding. This situation can occur in a number of pathologies. Among them is a deficiency of vitamin K, necessary for the production of coagulation factors. Also, a decrease in the prothrombin index can be explained by the consumption of drugs that promote blood clotting. Such test results may also indicate that the patient has liver diseases in which the production of coagulation factors is impaired. Sometimes a decrease in the prothrombin index is a consequence of a congenital deficiency of some coagulation factors or a signal of a pronounced hereditary or acquired fibrinogen deficiency in the body. Another similar situation can be explained by dysbiosis and other intestinal ailments, protein metabolism disorders, certain pathologies of the kidneys and the entire urinary system, and even cancer of the gallbladder or pancreas.

What does an increase in the indicator mean??

If the prothrombin index is elevated, then such test results indicate too rapid blood clotting, in other words, hypercoagulation. This condition can be dangerous as it increases the risk of blood clots.

An increase in the prothrombin index can also be observed with liver diseases and vitamin K deficiency. Another such situation sometimes occurs when consuming anticoagulants, hormonal drugs (contraceptives), antibacterial agents, laxatives and other drugs.

An increase in the prothrombin index is also possible with leukemia and other oncological pathologies, as well as with a congenital deficiency of certain coagulation factors. Sometimes such test results are provoked by a parallel increase in the number of red blood cells in the blood.

During pregnancy, a noticeable increase in the prothrombin index warns of possible placental abruption, and a decrease in this indicator threatens the development of bleeding during pregnancy. labor activity or the first postpartum period.

Which is 95-105%, is one of the indicators characterizing the blood coagulation system. Blood clotting is very difficult process, carried out with the participation of a whole cascade of special proteins called coagulation factors. Activation of this process is possible in two ways - internal and external.

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

What does the prothrombin index mean?

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

1. Estimate the approximate activity of II, V, and VII and X coagulation factors
2. The value of this indicator is used to judge liver function.
3. About the saturation of the body with vitamin K
4. About general condition blood coagulation systems
5. Using this indicator, you can monitor the effectiveness of anticoagulant therapy.

How is the prothrombin index determined?

The prothrombin index is determined in the capillary or venous blood. In the second case, fasting blood is taken into a test tube with an anticoagulant in a ratio of 9:1. Sodium citrate is used as an anticoagulant. In the laboratory, the blood is centrifuged. The resulting plasma is used to determine prothrombin time (PT). The normal PT ranges from 12 to 20 seconds, depending on the activity of thromboplastin, which is used during the reaction in a given laboratory.

PI = PV healthy/PV sick. X 100 (normal 95-105%)

Clinical significance PI

With increased coagulation, PT, or prothrombin, the norm of which is from 12 to 20 seconds, shortens, and PI increases. This can happen during pregnancy, during massive trauma, when a lot of tissue thromboplastin enters the blood.

On the contrary, PT increases and PI decreases when coagulation decreases, for example in the case congenital deficiency coagulation factors, with serious illnesses liver, with a lack of vitamin K (it can occur with cholestasis, dysbacteriosis, impaired intestinal function). PI decreases with or its functional inferiority, with DIC syndrome, in the presence of substances that inhibit coagulation.

What is INR

Treatment with indirect anticoagulants naturally reduces the prothrombin index. Each laboratory may have its own norm. Therefore, in order to be able to compare test results obtained in different laboratories, a standardized test such as INR was introduced. This calculated indicator. It is determined based on the ratio of the patient’s prothrombin time, the normal PT value and the degree of thromboplastin sensitivity index (TSI).

INR=(PT b-th/PT norm) to the degree of MICH

In a healthy person, the INR is within the range of 0.8-1.2.

This indicator is used to monitor the effectiveness of anticoagulants. When treated with anticoagulants, when coagulation is reduced (for example, after heart surgery), the INR should be increased to 2-3. As coagulability increases, the INR decreases. The relationship between PI and INR is such that as PI decreases, the INR increases.