Coagulogram: what is this analysis and what is it for?
The content of the article:
- Indications for coagulogram
-
The main indicators of the coagulogram, their normal values and deviations from the norm
- Clotting time
- Fibrinogen concentration in blood
- Activated partial thromboplastin time
- Activated recalcification time
- Prothrombin index
- Thrombin time
- The number of soluble fibrin-monomeric complexes
- How to properly prepare for a coagulogram
- Research methods
- Blood clotting
A coagulogram (hemostasiogram) is a blood test for hemostasis, a study of the ability of blood to clot.
A set of interacting regulatory mechanisms provides a normal blood environment. So, the coagulation system is responsible for the processes of coagulation (coagulation), prevents and stops bleeding, the anticoagulant system provides anticoagulation, and the fibrinolytic system promotes the dissolution of blood clots. Homeostasis is a system that ensures the constancy of the internal environment of the body, one of its divisions is hemostasis - maintaining a balance between coagulating and anticoagulant blood factors. Violation of hemostasis leads to pathological thrombus formation or increased bleeding.
Indications for coagulogram
The most common study that is prescribed to study the hemostatic system is a coagulogram, which includes determining the time required to stop bleeding and the factors of this system.
Coagulogram allows you to assess the state of the blood coagulation system
Indications for the appointment of a coagulogram:
- diagnosis of blood clotting disorders;
- planned examination before surgery;
- gestosis;
- high risk of thrombosis, predisposition to thrombosis;
- injuries accompanied by bleeding;
- diseases of the cardiovascular system;
- bone marrow lesions;
- varicose veins of the lower extremities;
- autoimmune diseases;
- chronic liver and spleen diseases;
- diseases with hemorrhagic syndrome;
- chronic anemia;
- control of thrombolytic therapy;
- examination before prescribing hormonal contraceptives, anticoagulants and some other groups of drugs.
The main indicators of the coagulogram, their normal values and deviations from the norm
The basic coagulogram includes seven indicators, which together allow you to assess the state of all systems that affect blood coagulation. The expanded coagulogram, which is prescribed for some diseases, includes a larger number of indicators.
Clotting time
Blood clotting time - the time interval from the moment blood is taken from the vessel to the formation of a blood clot. Characterizes the duration of bleeding from a wound. Its lengthening indicates a decrease in the activity of the hemostasis system, inhibition of the function of the blood coagulation system, and a decrease indicates a decrease in the activity of the antithrombin and fibrinolytic blood system, an increase in the activity of blood coagulation.
Normally, the clotting time of venous blood should be 5-10 minutes. Exceeding the normal blood clotting time can be caused by infectious, autoimmune diseases, diseases of internal organs, disseminated intravascular coagulation syndrome, endocrine disorders, intoxication of the body, and an increased level of platelets. A reduced coagulation index is detected in anemia, liver failure, cirrhosis, hemophilia, leukemia, lack of potassium and vitamin K, overdose of drugs with an anticoagulant effect. The value of the indicator also depends on the material of the test tube in which the indicator is determined.
Fibrinogen concentration in blood
Fibrinogen is one of the factors of the blood coagulation system, a glycoprotein that is produced in the liver. The protein is involved in the formation of blood clots, determines the viscosity (density) of the blood, and takes part in reparative processes.
An increase in the level of fibrinogen leads to the development of thrombosis, increases the risk of developing cardiovascular diseases. Fibrinogen belongs to the acute phase proteins, an increase in its concentration in the blood is detected in inflammatory diseases of the liver and kidneys, pneumonia, the development of tumor processes, disorders in the thyroid gland, burns, stroke, myocardial infarction. A decrease in its content occurs with disseminated intravascular coagulation syndrome, hepatitis or cirrhosis of the liver, hereditary fibrinogen deficiency, chronic myeloid leukemia, lack of vitamins K, B and C. A low concentration of fibrinogen in the blood may be due to the intake of anabolic steroids and fish oil.
The indicator evaluates the content of 1 g of fibrinogen in 1 liter of blood. The norm in adults ranges from 2 to 4 g / l.
The fibrinogen content in women increases during menstrual bleeding and during pregnancy. The physiological level of fibrinogen during the gestational period increases every three months; by the third trimester, its values can reach 6 g / l. In the case of severe complications of pregnancy (placental abruption, amniotic fluid embolism), its concentration in the blood decreases.
In newborns, a relatively low level of fibrinogen is noted: 1.25–3 g / l.
Activated partial thromboplastin time
APTT, activated partial thromboplastin time, is the period required for a blood clot to form.
The indicator is determined by imitating the blood coagulation process. In the course of such a study, reagents-activators (kaolin-cephalin mixture, calcium chloride) are added to the blood plasma and the time during which a fibrin clot is formed is determined.
Normally, APTT is 30–45 s. An increase in the indicator is observed with a decrease in blood clotting, vitamin K deficiency, autoimmune pathologies, idiopathic thrombocytopenic purpura, and liver diseases.
Activated recalcification time
ABP, activated recalcification time - the time required for clot formation after addition of calcium salts. The study is carried out by saturating the plasma with calcium and platelets. The norm is 60-120 p.
The lengthening of the AVR is possible with an insufficient number of platelets (thrombocytopenia) or their functional inferiority (thrombocytopathy), with hemophilia, in the second stage of DIC syndrome.
A decrease in AVR indicates a tendency to increased thrombosis, the development of thrombosis, thrombophlebitis.
Prothrombin index
PTI, prothrombin index is the ratio of the standard prothrombin time to the prothrombin time of the analyzed blood sample, expressed as a percentage. The norm is considered to be 97-100% PTI, an increase indicates an increased risk of thrombus formation, a decrease indicates the possibility of bleeding.
The results of determining the prothrombin index may differ depending on the type of reagent, at present this indicator is considered outdated; instead, a more stable indicator is used - INR, the international normalized ratio, determined using a special standardized tissue factor.
Thrombin time
Thrombin time is the period during which the conversion of insoluble fibrin from fibrinogen occurs. The norm is 10–20 s. Thrombin time above normal is observed with a decrease in the level of fibrinogen, with an increase in the activity of the fibrinolytic system, as well as when taking anticoagulants. An indicator below normal is associated with an increased amount of fibrinogen in the blood.
The number of soluble fibrin-monomeric complexes
RFMC, soluble fibrin-monomeric complexes - a transitional link between fibrinogen and fibrin. The normal content of RFMK in blood plasma is 3.36–4 mg per 100 ml of plasma. An increase is observed when an excessive number of microthrombi appear in the vascular bed. Evaluation of the RFMK concentration is important for intravascular blood coagulation, increased thrombus formation, diagnosis of disseminated intravascular coagulation, and is often used to assess the effectiveness of anticoagulant therapy.
If necessary (usually when certain indicators deviate from the norm), an extended examination is performed after the base coagulogram. The extended coagulogram includes indicators of the baseline study and a number of additional indicators (D-dimers, antithrombin III, protein C, antibodies to phospholipids, etc.).
How to properly prepare for a coagulogram
Blood is taken for a coagulogram in the morning, on an empty stomach, 12 hours after the last meal. Preparation on the eve of the study is as follows:
- exclusion from the diet of spicy and fatty foods;
- to give up smoking;
- refusal to drink alcohol;
- limitation of physical and emotional-mental stress;
- Stop taking medications that affect blood clotting (such as aspirin)
You should inform your doctor about taking anticoagulants.
Research methods
The interpretation of the analysis, the time for preparing the results and the procedure for collecting material can vary significantly depending on the method used in a particular laboratory. There are two main methods - according to Sukharev and according to Lee-White. What is the difference between these methods and what does each of them show?
For analysis by the method of Sukharev, capillary blood is used, that is, one that is taken from a finger. The material is placed in a thin vessel called a capillary. Shaking the vessel, the laboratory assistant marks the time and marks in a special table the moment when the movement of blood slows down and stops. These indicators with normal blood clotting are 30-120 s (the beginning of coagulation) 3-5 minutes (the end of coagulation). Blood for analysis by Lee-White is taken from a vein. The time it takes for a dense blood clot to form is estimated. Normally, this time is from 5 to 10 minutes.
To determine the concentration of fibrinogen, thrombin time and other parameters of the coagulogram, only venous blood is used.
How many days is the coagulogram done? As a rule, it takes from several hours to a day to prepare the results.
Blood clotting
Blood clotting involves platelets (platelets), proteins, potassium ions, and a group of plasma enzymes called clotting factor. When the integrity of the circulatory system is violated, physiological activation of platelets occurs, their swelling and sticking together (aggregation) and simultaneous adhesion (adhesion) to other surfaces, which allows platelets to be retained in the places of exposure to high blood pressure. An increasing number of platelets are involved in the process, and substances that activate plasma hemostasis are released. As a result of a chain of sequential reactions involving blood coagulation factors, a platelet plug is formed on the damaged part of the vessel. Such a hemostatic plug is able to withstand the effects of high blood flow velocity,serves as a barrier to the penetration of pathogenic agents, prevents further blood loss.
The blood coagulation system ensures the integrity of the circulatory system
The triggering mechanism for the formation of a platelet plug depends on the site of tissue injury: in response to damage to the skin, a clot is formed along the external pathway of activation of blood coagulation, in case of damage inside the body, a thrombus is formed (internal pathway of activation of blood clotting).
During the formation of a blood clot under the influence of thrombin, the protein fibrinogen is converted into an insoluble substance fibrin. After a while, a spontaneous contraction of the fibrin clot occurs and the formation of a red thrombus, consisting of fibrin fibers and blood cells. The activation of the fibrinolytic system (antipode of the coagulation system) and the synthesis of anticoagulants (heparin, an inhibitor of the tissue coagulation pathway, proteins C and S, antithrombin III, antitrypsin, alpha2-macroglobulin, etc.) prevent the further spread of the thrombus formation process along the vascular bed. These substances are synthesized in the body following the blood coagulation process and are excreted into the bloodstream at a certain rate.
The increase in the anticoagulation potential of the blood ensures the maintenance of the blood in a liquid state. Decreased activity of anticoagulants can cause prolonged and profuse blood loss.
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Anna Kozlova Medical journalist About the author
Education: Rostov State Medical University, specialty "General Medicine".
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