normal rate, how to measure it?

The INR (International Normalized Ratio) is a blood clotting indicator. This marker makes it possible to monitor certain factors involved in blood coagulation. Generally, it is prescribed to monitor patients treated with an anticoagulant. What is the INR? What is the standard rate? What does a rate that is too low or too high mean? What to do ?

Definition: what is the INR?

INR (International Normalized Ratio) is a blood clotting indicator. It is measured by comparing the patient’s clotting time to that of an “international” control patient. This marker allows you to monitor certain factors involved in blood clotting. Generally, it is prescribed to monitor patients treated with an anticoagulant: vitamin K antagonist. As the effect of this anticoagulant is quite fluctuating, the dosage must be carried out regularly. Thus, depending on the result, the treatment can be adapted. INR makes it possible to compare the prothrombin time of a patient to the control patient. Thus, the figure obtained will remain the same depending on the laboratory.

What is the normal INR level?

“It depends on the clinical situation of the patient, usually the target is between 2 and 3 for the vast majority of patients, except some patients who have heart valves or other pathologies requiring higher values between 3.5 and 4.5 for example, the medical biology laboratory must indicate the targets to be reached“, explains François Blanchecotte, President of the Syndicate of Biologists. The latter advises above all to know the target indicated by the attending physician or the cardiologist. “If you are on target [INR normal]no problem: you continue to take the dose indicated by your doctor.”

What is an INR that is too low or too high?

“If you stray from the targettwo cases, indicates François Blanchecotte. Vohyou are between 0 and 2, your blood is not fluid enough, you should contact your doctor to correct the dose and increase it, if you are above the target your risk of bleeding increases by 50% each time you increase by one unit example for 4.0 you are above with an increased risk of 50%, it must be reduced, again your doctor must correct it“, recommends François Blanchecotte.

The INR assay should only be repeated 48h to 72h after the dose change, not the next day. Indeed, the drug will not have had time to act yet. Like Préviscan, the effect of which persists after several days of discontinuation. THE Previscan is an oral anticoagulant belonging to the family of vitamin K antagonists. This medication prevents clots from forming. Depending on the result of the INR assay, the doctor can adapt the precise dosage of the drug. If the INR is too low, the action of the drug is certainly insufficient. Conversely, if the INR is too high, the patient certainly has an overdose.

Thanks to François Blanchecotte, President of the Union of Biologists.