Prothrombin time or PT is a blood test that assesses the ability of the blood to clot, that is, the time needed to stop bleeding, for example.
Thus, the prothrombin time test is used whenever frequent bleeding or bruising occurs to try to find the cause of the problem, as well as when there are suspicions of liver problems, being also asked to measure TGO, TGP and GGT, for example. See which tests assess the liver.
In the case of people who use oral anticoagulants, such as Warfarin or Aspirin, the doctor periodically requests the INR, which is a more specific measure than the TP to assess the effect of the drugs, since the TP is usually high in these conditions.
Prothrombin, also known as coagulation factor II, is a protein produced by the liver and when activated promotes the conversion of fibrinogen into fibrin, which, together with platelets, forms a layer that prevents bleeding. Thus, prothrombin is an essential factor for blood clotting to happen.
Reference values
The prothrombin time reference value for a healthy person should vary between 10 and 14 seconds. In the case of INR, the reference value for a healthy person should vary between 0.8 and 1.
However, in the case of using oral anticoagulants the value must be between 2 and 3, depending on the disease that led to the need for treatment with this type of medication.
Meaning of the results
The prothrombin time test result may be altered due to different causes, so whenever there are changes, the doctor may order new tests to be able to identify the correct cause and start treatment.
Some of the most common causes include:
High prothrombin time
This result indicates that if a cut occurs, bleeding will take longer to stop, with some of the most common causes including:
- Use of anticoagulants; Alteration of intestinal flora; Poorly balanced diet; Liver diseases; Vitamin K deficiency; Coagulation problems, such as hemophilia;
In addition, some medications such as antibiotics, corticosteroids and diuretics can also change the value of the test, so it is advisable to inform the doctor about all the medication you are using.
Low prothrombin time
When prothrombin value is lower it means that coagulation happens very fast. Thus, although bleeding is more rare and stops quickly, there is an increased risk of clots that can lead to infarction or stroke.
Some of the causes that can cause this change include:
- Use of vitamin K supplements; Excessive consumption of vitamin K foods, such as spinach, broccoli or liver; Use of estrogen tablets, as a birth control pill.
In these cases, it may be necessary to start the use of anticoagulants or heparin injections until the cause of the change is identified. After that, the doctor will recommend the most appropriate treatment.
