Diagnosis

INR

definition

The INR value is a value from laboratory medicine. It is used to assess a certain section of blood coagulation, namely extrinsic blood coagulation. So it describes how quickly the blood coagulates. In a figurative sense, it measures to what extent and how quickly the body is able to close the bleeding source after an injury and thus stop the bleeding. In healthy people, the INR value is around 1.0. If the blood clotting lasts longer than normal, the INR value increases and the risk of bleeding increases accordingly.

The INR value has replaced the previously known Quick value. The reason for this is that the Quick value not uniformly recorded so there were fluctuations in the value depending on the laboratory in which the test was carried out. The INR, on the other hand, is a uniformly recorded value. The uniformity can already be found in the name. INR actually means "international normalized ratio".

Of the Quick value and the INR value behave inversely proportional to each other. A high Quick value means a low INR value. In therapy with an oral anticoagulant, i.e. a blood thinner from the group of Vitamin K antagonists, the INR is affected. This group includes, for example, the drug Phenprocoumon, which is sold under the name Falithrom or Marcumar® is known. It is used for example in patients with Atrial fibrillation, thrombosis or Pulmonary embolism, such as artificial heart valves used to thin the blood sufficiently to prevent a blood clot from forming.

Read more about the topics here: Quick-Wert and Marcumar®

What is the INR used for?

The INR value is required in everyday clinical practice to monitor the blood of patients who are taking the blood thinner Phenprocoumon (better known as falithrom or Marcumar®) take. Most patients suffer from atrial fibrillation or have an artificial heart valve. The drug is used to thin the blood and is supposed to prevent blood clots from forming. These can lead to atrial fibrillation, for example stroke to lead. However, a common side effect of the blood thinning drug is the tendency to bleed. The patient must therefore be adjusted so that no bleeding occurs despite the blood thinning.

This requires a value that tells the attending physician how the patient is currently prepared for the drug. So it's similar to measuring the blood level of a drug to find out how much of it is currently in the body. This value is the INR value. The normal value for healthy people is around 1.0. After adjusting to the blood thinner, the value should increase. How much the value increases depends on the disease that is being treated with the drug. If the value is too low, there is a risk of a blood clot forming. If the value is too high, there is a risk of potentially serious bleeding.

Difference between INR and Quick values

The Quick value and the INR value basically describe the same thing, namely how quickly the blood coagulates. The Quick value has been used for many years but has the disadvantage that it not standardized and so can vary from laboratory to laboratory. The newer INR value was developed to address this problem. It is, so to speak, a standardization of the Quick value. The two values are related inversely proportional to each other. This means that the INR value increases as the Quick value decreases and the INR value decreases as the Quick value increases.

INR too high

If the INR value is too high, i.e. above the target range, it increases Risk of unwanted bleeding. This can be banal bleeding, such as Epistaxis or rebleeding after minor injury. However, it can also cause serious bleeding. examples for this are Bleeding in the gastrointestinal tract and the Cerebral hemorrhage. Such bleeding can be potentially life threatening. If the INR value is too high, it can also show up as bruises.

INR value when taking Marcumar®

The range in which the INR value should lie does not depend on the drug administered (Marcumar®) differ from the disease to be treated. Depending on which illness is associated with taking the Marcumar® should be able to be treated Target values between 2.0 and 4.5 to be necessary. You are just beginning to adjust to the drug Close controls of the INR value are urgently required, To avoid overdosing on the one hand and underdosing on the other.

Measurement of the INR value

In order to determine the INR value as part of a normal blood test in the laboratory, a blood tube with citrate is removed. The citrate ensures that the blood after the withdrawal does not curdle directly. Once in the laboratory, the blood coagulation is triggered and the time is measured. This time is called Prothrombin time designated. The prothrombin time is then converted into an INR value by an appropriate device.

INR meter for the home

Since some patients need to measure the INR value relatively frequently, there are devices for measuring INR that the patient can use at home. So he does not have to go to the family doctor for every INR value check. These devices work in a similar way to the devices for measuring blood glucose in patients who are on one Diabetes mellitus (Diabetes). A test strip is inserted into the device and a drop of blood is applied to it. After a few seconds the device displays the INR value. After training the patient, he can use the INR measurement MarcumarDetermine the ® dose yourself adequately.

Costs that are covered by the health insurance

The health insurance pays the so-called Coagulation self-management under certain conditions. The blood-thinning medication usually has to be taken for life. The main indication is the presence of one artificial heart valvethat requires permanent blood thinning. For other diseases such as the Atrial fibrillation, other factors must apply in order for self-measurement approval to be granted. Such factors are, for example, the occurrence of complications with the previous INR setting or difficulties for the patient to visit the doctor's office regularly due to the need for care or a long journey to the doctor's office. Even if a permanent blood thinning is necessary in children, an INR measuring device can be approved by the health insurance company. However, the requirements are always individually assessed by the health insurance company.

Causes of a low INR value

The main causes of low INR values during therapy with a blood thinner such as Falithrom are primarily one wrong diet and Drug interactions. The drug Marcumar® is one of the vitamin K antagonists, which means it inhibits the effect of Vitamin K. However, some components of the blood clotting system need vitamin K in order to function. If there is not enough vitamin K, the bleeding time is increased. If, for example, a lot of vitamin K is supplied with food, this has the opposite effect. Blood coagulation is started up again. Therefore, patients should use the Marcumar® you know roughly which foods contain a particularly high amount of vitamin K and which ones Consume only in moderation. Foods containing vitamin K include a few in particular Cabbage and spinach. Yet there are also numerous drugs that can have the effects of Marcumar® and thus can lower the INR value. These include, for example cortisone, Digitoxin and Digoxin, Johannis herbs, Metformin and haloperidol.

INR target values for specific diseases

How high the INR needs to be depends on the condition that requires blood thinning. The table below shows the main INR target values. For some indications, such as the mechanical aortic valve, the INR target value depends on other risk factors. Atrial fibrillation is one of the risk factors. If there is also atrial fibrillation, the INR should be between 2.5 and 3.5 for a mechanical aortic valve.