The function of blood is to maintain homeostasis
Blood is the most important biological fluid body. Blood controls homeostasis (consistency is called internal environment body), is a transport medium, protects the body from foreign substances. Its normal density is maintained by a system that works in two directions:
- clotting effect - promotes thickening and thrombus formation;
- anticoagulant effect - maintains blood in a liquid and fluid state. .
When the balance of these two mechanisms is disrupted, a person becomes more prone to blood clots or bleeding.
Characteristics of the extrinsic coagulation pathway - INR
Blood thickness is regulated by the protein prothrombin, which is a precursor to the blood clotting factor thrombin. It is synthesized in the liver with the participation of vitamin K. To determine the level of prothrombin, modern doctors use several research methods:
- PTV and PTI.
- Prothrombin level according to Quick.
INR (stands for) International Normalized Ratio is a standardized measurement used to express the results of a test of prothrombin time and blood clotting rate.
Until 1983, only prothrombin time (hereinafter referred to as PTT) was used to determine the rate of coagulation - this is the period during which a thrombus is formed from fibrin threads, clogging mechanical damage to blood vessels and preventing bleeding. To calculate the PTV, laboratories used different types reagents from different manufacturers, due to which test results differed between institutions. In order to level out this connection to the standards of a particular laboratory, WHO decided to introduce an INR indicator.
INR norm
Normal indicators depend on many factors
The INR norm for healthy patients and people taking direct-acting blood thinning drugs is 0.8-1.2. This indicator is standard and relevant for most countries of the world. However, it is worth considering that in some cases INR standards may differ from generally accepted ones:
- The INR norm for pregnant women is 0.8-1.25.
- The INR norm for those taking blood-thinning medications with indirect action is 2.0-3.0.
- The INR norm for people with artificial valves or APS is 2.5-3.5.
The INR level plays an important role for pregnant women, since sudden jumps in this indicator can cause spontaneous abortion. For this reason, the INR is monitored throughout pregnancy.
Indications for prescribing an INR analysis
Liver cirrhosis - indication for analysis
Often, determination of INR is necessary in a complex study (this complex includes ACTV, PTV and PTI - prothrombin index, fibrogen and D-dimer analysis) for the speed and quality of blood clotting. Determination of INR is an obligatory part of the diagnosis of congenital or acquired forms of blood clotting deficiency. There are other medical indications for conducting an INR study:
- frequent and uncontrolled bleeding;
- PE (blockage pulmonary artery);
- myocardial infarction;
- thrombosis of deep veins or various organs;
- long-term and severe liver diseases (cirrhosis, hepatitis, etc.);
- DIC syndrome (at the first stages as a diagnostic method and then to monitor treatment).
It is imperative to monitor the INR for people taking anticoagulants and coagulants (especially warfin-based medications). Depending on the indicator, the dose of medications taken by the patient varies and his condition is assessed.
Preparation for analysis and methodology for its implementation
In order for the results of the analysis to be reliable, you should prepare for it. The patient needs:
- A few days before the test, avoid heavy physical activity, physiotherapy, massages, intravenous or conventional injections.
- If a person is being treated with anticoagulants, at 17:00 (approximately) the evening before the test, he should take all daily dose medicines.
- Have your last meal at least 8 hours before the test. In the morning before the test, you can drink regular still water.
The biomaterial for analysis is venous blood, which must be taken only from a peripheral vein. After blood is drawn in a laboratory setting, the sample is mixed with a preservative, which prevents the blood from clotting by binding calcium ions. The blood plasma is then separated from the sediment to obtain pure blood serum.
The next step involves neutralizing the preservative in the serum with potassium and adding thromboplastin, which will stimulate plasma clotting. The laboratory assistant calculates the time it took for clotting. The resulting indicator will be called prothrombin time.
After determining the prothrombin time, the INR is calculated using the standard formula. The analysis usually does not take much time; in most laboratories, results can be obtained within 1 day.
People taking coagulants or anticoagulants should have an INR test every 2-3 weeks. Usually this time is enough to select the correct dose of the drug. After determining the dosage of the medication, the test should be retaken every 6-8 weeks.
Elevated INR
Increased INR occurs in von Willebrand disease
An increase in the INR (provided that the person is not taking coagulants or blood-thinning medications) may indicate the presence of certain disorders in the body:
- liver pathologies;
- von Willebrand disease, hemophilia A/B type and other disorders of the coagulation mechanism;
- fat malabsorption disorder;
- complications after extensive blood transfusion;
- violation of bile reflux into the duodenum;
- hemorrhagic disease in newborns;
- lack of vitamin K in the blood.
An increase in INR often occurs with prolonged or intensive use of antibiotics (especially diclofenac and blemarene), synthetic hormones thyroid gland, anabolic steroids and anti-gout drugs.
A severely elevated INR (where 6 is critical) is dangerous condition. Such a violation may indicate the development of bleeding of varying intensity and location. For diagnoses such as ulcerative-erosive lesions of the gastrointestinal tract, inflammatory diseases of the stomach and intestines, hypertension, pathologies of cerebral vessels, kidney disease, an increased INR is extremely undesirable.
How to downgrade?
The main way to lower the INR is to take coagulants, but such medications must be taken strictly under the supervision of a doctor. Therefore, with an elevated INR level, patients are always hospitalized.
Reduced INR
Hematocrit deviations are the cause of changes in INR levels
The reasons for a decrease in INR levels or hypocoagulation may be:
- decrease or increase in hematocrit (volume of red blood cells in the blood);
- increased concentration of antithrombin 3 in the blood (an inhibitor of a number of blood clotting factors);
- violation of analysis methods (blood sampling from central vein instead of peripheral) or improper storage biological material(long-term exposure of blood plasma at a temperature of +4C);
- treatment with anticonvulsants, diuretics, contraceptives, corticosteroids.
If a low INR is detected in a person taking indirect anticoagulants, a dose adjustment of the medication is required.
With hypocoagulation, the level of thrombus formation significantly increases, which is fraught with the development of thrombosis of various vessels and organs.
How to increase?
Anticoagulant drugs are used to increase INR levels and further thin the blood. To prescribe them and determine the appropriate dose, you should consult a doctor.
Blood INR - this is one of the main indicators of a coagulogram blood test. A coagulogram allows you to examine blood according to 2 parameters: determine the rate of its clotting and identify the level of fibrinogen in it.
The rate of coagulation is determined by the INR test (international normalized ratio), otherwise INR is also called a test for the level of prothrombin (a protein that characterizes the blood clotting process). This test is done by comparing a patient's blood sample with a standard blood sample.
How are INR levels and blood clotting rates related? It’s very simple: the lower the INR level, the higher the rate of blood clotting (the blood is thicker) and, conversely, the higher the INR, the lower the rate of clotting (the blood is thinner).
INR test is effective method diagnostics and control of diseases that are directly related to an increase in blood density and the formation of blood clots in blood vessels: pulmonary embolism, thrombophlebitis, as well as complications arising from myocardial infarction and coronary insufficiency.
In medicine, there are specially accepted blood INR norms, which vary depending on whether the patient has a particular disease:
- U healthy people INR norm: 0,85 — 1,25 .
- If a patient has pulmonary embolism, then the normal INR in his case is: 2,0 — 3,0 .
- If you have a heart defect or venous thrombosis norm: 2,0 — 3,0 .
- For vascular pathologies, the INR norm is: 3,0 — 4,5 .
An increase or decrease in these indicators entails serious consequences for the entire organism.
Increase and decrease in INR: causes and consequences
Promotion blood INR levels occur for the following reasons:
- Deficiency of factors responsible for blood clotting.
- Leukemia in acute form.
- Lack of vitamin K in the body.
- Presence of abnormalities in liver function.
- Course of treatment with warfarin.
- Presence of syndromes: DIC, antiphospholipid, toxic shock, nephrotic syndrome.
- Presence of pancreatic adenoma or cancer.
- Malabsorption.
- Insufficiency of the heart muscle.
- Obstruction of the biliary tract. Jaundice.
Alcoholic beverages and some may also increase the INR level. medical supplies And fatty foods. The main consequence of an increase in INR is the threat of bleeding (both internal and external).
Demotion blood INR level occurs:
- In the last trimester of pregnancy.
- On initial stage deep vein thrombosis.
- At increased activity Factor VII.
- With DIC syndrome.
- In the presence of benign tumor blood.
Vomiting, diarrhea, excess vitamin K (if taken from food) and some medicinal preparations. Low level INR threatens the formation of blood clots.
INR norm when taking warfarin
Determining the INR level is mandatory procedure for patients taking a special drug to slow down the blood clotting process (warfarin) due to the fact that their body is prone to increased formation of blood clots. These patients have their own INR standards.
First, let's figure out what kind of drug this is. Warfarin is an anticoagulant that reduces the rate of blood clotting. It is prescribed to patients with diseases and conditions in which the occurrence of blood clots is especially dangerous: various thromboses, the presence of cardiac prostheses, pathologies of the heart muscle valves, myocardial infarction, pulmonary artery embolism, cardiac arrhythmias.
The action of this drug occurs as follows: the process of absorption of the drug takes place in the stomach and small intestine; Once in the blood, Warfarin reduces the formation of factors in the body that promote blood clotting. Due to this, the blood clots more slowly, becomes more fluid, and the risk of blood clots is reduced.
INR norm when treated with warfarin: 2,0-3,0 . Warfarin is taken once a day. Its dose is always selected individually, and sometimes the process of selecting the appropriate dosage can last up to 3 weeks. At this time, the patient needs to regularly determine his INR value. When the required dose of the drug is selected, you need to check the INR once every 2 weeks.
Attention! IN following cases An additional check of the INR level must be carried out: during treatment colds, when changing the usual diet, after changing place of residence (moving to another climatic zone).
A decrease in INR threatens the development of a stroke, and an increase threatens with hemorrhage in the brain. That is why, when taking warfarin, it is very important not only to constantly monitor the INR (take a test in the laboratory or measure the INR at home using a special device), but also always coordinate with your doctor the use of other medications, as well as follow a special diet.
Diet
When treating with warfarin, it is recommended to introduce foods containing increased amounts of vitamin K into your daily diet. This is necessary to weaken the effect of the drug. If there is not enough vitamin K, the effect of warfarin will increase and there will be a risk of bleeding.
Higher doses of vitamin K contain (in decreasing order): green tea, spinach, watercress, soybean oil, broccoli, lettuce, white cabbage, head lettuce, beef liver, cauliflower, green tomatoes, beans, cheese, cucumbers, zucchini, butter, potatoes and chicken eggs.
In conclusion, we would like to add that if your INR is always within the normal range when taking warfarin, this does not mean that you need to stop monitoring it. In any case, INR measurements should be carried out regularly, and if symptoms such as changes in the color of stool to black, nosebleeds or bruises appear on the body, you should immediately consult a doctor.
Not everyone knows about the INR blood test and what it is. The abbreviation INR stands for International Normalized Ratio. This indicator demonstrates how the human blood coagulation system functions. Such a study may be prescribed during anticoagulant therapy for individuals who are at risk of thrombosis. If a person is taking anticoagulants indirect type, then an INR test should be performed every two weeks.
INR is an indicator that shows prothrombin time. This indicator was introduced so that the assessment of the effect of anticoagulants on prothrombin time would be carried out uniformly. Accordingly, the doses of anticoagulants could also be prescribed uniformly. If the INR is prescribed in the analysis, it is safe to say that the results when determining PT can be compared. This allows for more precise monitoring of therapy when using indirect anticoagulants.
To diagnose problems associated with blood clotting, the PT indicator is used, which is expressed in seconds. If PT is determined in the laboratory to evaluate warfarin treatment, the INR should be used.
This indicator helps express results, regardless of which thromboplastin preparations are used by the laboratory. To calculate the INR, the patient's PT and his normal indicator . The patient's value is divided by the normal value. This way the prothrombin ratio is determined. Next, the result must be raised to a power. Its indicator is selected in accordance with the international sensitivity index. When selecting the dose of anticoagulants, it is necessary to maintain the INR at required level
. Of course, recommendations depend on the disease. Most often in clinical practice
Doctors prefer warfarin. This indirect anticoagulant is very popular. In this case, it is recommended to combine the analysis with the determination of APTT.
Blood sampling and results For analysis to determine the INR, people are most often sent who are permanent basis take indirect anticoagulants. For analysis, blood is drawn on an empty stomach. The intake on an empty stomach is prerequisite
. Blood is drawn from a peripheral vein. Within the sampling technique itself, there are no differences from the same biochemistry. When interpreting the results, one rule is used - the higher the INR result was demonstrated, the more liquid blood
- at the patient. There are three interpretation options:
- INR in accordance with normal values;
- INR is higher than normal;
INR is below normal.
If the INR is within normal limits, then we can conclude that there are no problems with anticoagulant therapy. The treatment is carried out correctly, and the dose corresponds to adequate indicators. In this case, the reception must continue in the existing mode.
If the INR is elevated for some reason, then we are most likely talking about an overdose. In this case, the dose should be reduced, since too high a percentage of dilution can cause bleeding, including internal bleeding.
If the INR does not correspond to normal values, being below the required level, then there is no effective result from treatment with anticoagulants, the blood does not thin. In turn, this state of affairs is an excellent breeding ground for thrombus formation. In such cases, the dose of the drug should be increased. Talking about, the INR in individuals who do not take anticoagulants should normally range from 0.8 to 1.15. If the indicator is in the range from one and a half to two, then we are talking about the need to prevent thrombus formation in the heart, regardless of the type atrial fibrillation.
An indicator of 2-3 is observed when prophylaxis is necessary after surgery in persons at risk. Preventive actions in this case, they should be performed in case of damage to the heart valves, in case of complications due to myocardial infarction.
With an indicator of three to four, treatment of thromboembolic lesions that are present in the peripheral main arteries is required. With an indicator of up to 4.5, we can talk about the prevention of thrombosis after surgery, during which any prosthesis was introduced into the cardiovascular system.
Proper preparation and information for pregnant women
It was already mentioned above that blood is taken for such an analysis from a vein. This must be done in the morning; the collection must be preceded by at least an eight-hour fast. At the same time, the total hours of hunger should not exceed 14. Limit yourself to pure drinking water You can't live without gas.
During the day, it is best to limit yourself to heavy foods in order to prevent food overload. Drinking alcohol at this time is also not recommended. For half an hour before blood sampling, it is necessary to eliminate psycho-emotional and physical stress. It is also necessary to limit smoking.
However, there are factors that can affect the results of the study, and in particular lead to incorrect numbers. The analysis result can be distorted by incorrect actions of the laboratory assistant and lack of proper preparation. In particular, if the tube is not filled with enough blood or the anticoagulant is not mixed well, it will not be possible to obtain relevant results. The same problems occur if there is a delay in sending a sample for testing.
Some laboratories may suggest using capillary blood for INR. However, such research is highly unreliable. This is due to the fact that tissue thromboplastins are often included in the sample. In case of incorrect blood sampling, and in particular, injury to a vein, hemolysis may occur, which will also not allow obtaining correct information. Determining INR during pregnancy is a mandatory test. Its importance is difficult to overestimate. During pregnancy, a woman's body undergoes a large number of changes. This includes the formation of a third circle of blood circulation, which is built from the uterus and placenta.
In this regard, the INR level during pregnancy always becomes higher than the normal norm, and the time for clot formation is reduced. Usually the indicators change at least twice. In the absence of bad tests, INR determination is performed once every trimester. If any problems are identified, the delivery is performed more often. A special course of therapy may even be prescribed.
Incorrect INR readings during pregnancy can lead to spontaneous abortion. Prothrombin times that are too long create a risk of bleeding during childbirth, which can also cause death. Low levels can lead to the formation of blood clots, which threatens not only the mother, but also the unborn child.
In a blood test for clotting important indicator The INR norm is the international normalized ratio. The indicator allows you to measure the rate of sedimentation of blood cells and the formation of clots. The marker is under constant monitoring by doctors in the case of special therapy aimed at preventing blood clots.
Blood clotting is a protective reaction of the body
What does INR show?
The international normalized ratio shows the state of the blood coagulation system - hemostasis. The measurement occurs through special calculations, in which the prothrombin index (PTI) and the international thromboplastin sensitivity index (ISI) take part. Thanks to INR, it is possible to accurately determine the amount of prothrombin in the blood and its compliance with reference values.
Indications for testing
An INR test is prescribed to evaluate when it is necessary to determine the cause of severe bleeding or, conversely, higher level blood clot formation.
The main indications for such a blood test are:
- control of treatment with direct anticoagulants (blood thinners);
- heavy pathological changes in the liver – cirrhosis, hepatitis;
- therapy with indirect antithrombotic drugs;
- cardiac and vascular pathologies – great importance have analysis results for atrial fibrillation (atrial fibrillation), ischemia, stroke;
- pregnancy;
- gestosis.
Using this method of blood testing, doctors can promptly identify abnormalities in the patient’s condition and prescribe corrective treatment. And in the case of constant use of the drug Warfarin or other anticoagulants, the required dose of the drug is selected based on the INR level.
Where to donate blood for INR?
It is possible to accurately determine the level of blood clotting using the assessment of prothrombin according to Quick and INR, therefore, when choosing medical institution this needs to be taken into account.
You can donate blood either in a private laboratory (for a fee) or in a regular clinic, if the level of qualifications of specialists and the availability of equipment allows.
Device for self-analysis of INR
It is quite possible to conduct the study at home, but for this you need to buy a special device - an express coagulometer. This option is more suitable for people who constantly take medications to reduce blood clotting. If you need a one-time test, it is better to contact the laboratory.
Preparing for analysis
The reliability of the INR test results is always accurate; the main thing is to properly prepare for the delivery of biological material.
- The last meal should be 7–8 hours before the procedure, since the biomaterial is collected on an empty stomach.
- The day before the procedure, do not overwork the body with heavy physical activity, avoid stress and emotional overstrain.
- Do not carry out medical manipulations– exclude IVs and injections – 48–72 hours before the procedure.
How is the INR test performed?
A blood test or coagulogram to assess the state of homeostasis takes place in several stages.
- Biological material is collected from a vein in the elbow.
- The resulting blood is placed in a glass tube and diluted with a preservative - citrate.
- The settled blood cells are separated from the plasma. The function of citrate at this stage is to bind calcium ions and prevent clot formation.
- PTI is calculated. With the help of thromboplastin, the effect of the preservative is neutralized and the rate of clotting of pure plasma is observed.
- The international normalized ratio is calculated using a mathematical method.
Study time is 2–3 hours. Results can be obtained by evening or the next day.
INR norm and interpretation of results
Normal values in healthy people who do not take anticoagulants differ from those in patients who regularly use antithrombotic drugs. Slightly different values during pregnancy, and sometimes there are differences by age.
Table “INR norm for different categories of people"
Deviations in the INR in the coagulogram downward or upward indicate the development of negative abnormalities in the patient’s body.
When is the INR norm different for women than for men?
Normal INR values in women may differ from those in men if the woman’s hormonal levels undergo changes. This happens in 2 cases:
- during pregnancy;
- when taking hormonal contraceptives.
In such situations, values may greatly exceed the reference limits. If there is a constant increase, there is a need for special therapy.
Reasons for deviations from the norm
A rise or fall in the international normalized ratio indicates development pathological conditions in organism.
Table “Causes of deviations from the norm”
| Decrease in indicators | Increased amount of antithrombin |
| Negative effects on blood clotting of diuretics and contraceptive drugs | |
| Hematocrit abnormalities | |
| Increased blood viscosity | |
| Incorrectly selected dose of anticoagulants (if such drugs are taken regularly) | |
| Increasing values | Lack of vitamin K in the body |
| Liver diseases | |
| Disturbances in the normal absorption of fats in the intestine | |
| Deviations in hemostasis at the genetic level | |
| Negative reaction of the body to indirect anticoagulants |
Range of INR values depending on the dose of warfarin
Regardless of whether the indicators are higher than normal or lower, contacting a doctor is mandatory. High level INR is dangerous due to external and internal bleeding, and low INR is dangerous due to thromboembolic complications.Question answer
Warfarin analogues that do not require INR control
Among indirect anticoagulants, Warfarin is considered the most effective. It slows down blood clotting and increases INR. The only inconvenience of Warfarin is the constant monitoring of the international normalized ratio - once a week if the values are unstable and once every 14 days if the values are normalized. Therefore, the patient gives preference to analogues that do not require constant monitoring of the INR.
The most effective substitutes, Xarelto and Pradaxa, are prescribed for:
- thromboembolism;
- suffered a stroke;
- thrombosis.
Such analogues are not suitable for the treatment of lesions of the heart valves and in the presence of artificial valves. In addition, Warferon cannot be replaced with analogues without medical supervision.
The INR indicator helps to study the state of hemostasis and determine the rate of blood clotting. The marker is especially important during anticoagulant therapy. Here, the international normalized ratio allows you to monitor the patient’s condition and adjust drug doses in a timely manner. You can get tested for such a marker either in a specialized laboratory, a clinic at your place of residence, or at home.
