Does this test have other names?
Prothrombin time / PT, prothrombin time / international normalized ratio, PT / INR
What is this test?
Prothrombin time is one of several tests used to assess whether your blood is clotting properly. Blood clotting is necessary to help stop bleeding. Proteins in the blood called clotting factors (coagulants) help make the blood sticky and clot. They make it go from a liquid to a solid-state.
As soon as you begin to bleed, either internally or on the body’s surface, platelets in the blood collect around the bleeding area. Then platelets and clotting factors react to thicken the blood and stop bleeding. Blood problems, including deficiencies in clotting factors or platelets, can usually prevent the blood from clotting and cause abnormal bleeding.
The liver generally produces clotting factors. Prothrombin is a type of clotting factor. When bleeding occurs in any part of the body, prothrombin quickly turns into thrombin. The prothrombin time test is used to measure how quickly prothrombin converts to thrombin to stop bleeding. If the prothrombin does not convert at the average rate, the cause could be a blood clotting disorder.
The prothrombin time test can help diagnose inherited disorders and other conditions that can affect blood clotting. Among them are the following:
Vitamin K deficiency Deficiency in clotting factors I, II, V, VII, or X Liver diseases Hemophilia Bone marrow problems Von Willebrand disease Immune system problems Some types of cancer, including leukemia
Why should I have this test?
You may need it if you have symptoms of a bleeding disorder. They may include the following:
Abnormal menstrual periods in women Frequent nosebleeds Bleeding occurs more quickly. Bruises that form more easily Excessive bleeding The appearance of blood in the stool
You may need to have this test regularly if you take a blood thinner, such as warfarin. This is to make sure you are taking the correct dose.
You may also need this test before surgery or a procedure. This is to make sure that the blood is clotting generally not to have bleeding problems after the surgery or procedure.
What other tests could I have along with this one?
You may need other tests to measure the ability of your blood to clot normally. They may include the following:
Thrombin time test or TT Activated Partial Thromboplastin Time (aPTT) Other tests to measure different aspects of blood clotting, such as platelet function
Most likely, a healthcare professional will draw her child’s blood from a vein. First, she will clean the surface of your child’s skin with an antiseptic and place an elastic band (which will act as a tourniquet) on the upper arm to apply pressure and make the veins swell and fill with blood. . Next, she will insert a needle into a vein (usually on the inside of the elbow or the back of the hand) and draw and collect the blood in a vial or syringe. A chemical in the bottom of the vial or syringe will prevent the blood from clotting before the test starts.
After the procedure, the rubber band is removed. Once the blood is collected, the needle is removed, the area is covered with cotton to stop the bleeding, and plaster or small bandage is placed. Drawing blood for this test only takes a few minutes.
Taking a blood sample causes temporary discomfort, and the only thing the patient feels is a brief pinprick. After removal, a small bruise may appear, which should disappear after about a day.
Obtaining the results
Prothrombin time is measured in seconds. The results of the PT test are compared with the average clotting time of the healthy population.
Clotting time is longer in people who take blood-thinning medications. The blood sample is processed using a machine, and the results are usually available within a few hours or the next day.
The TP test is considered a safe yield. However, as with any medical test, some problems may occur during the blood draw, such as the ones listed below:
fainting or dizziness hematoma (collection of blood under the skin causing a lump and bruise) pain caused by multiple punctures when the technician is struggling to find the vein
Help your child
Blood draws are relatively painless. Still, many children are afraid of needles. By explaining the procedure to your child in terms that are easy for him to understand, you may help ease some of his fears.
Let your child ask the extraction technician any questions she may have. Tell him to relax and stay still throughout the procedure because if he were too tense his muscles or move, the removal would be more complex and more painful. It may also help to look away as the technician inserts the needle into your skin.
What do my test results mean?
Test results may vary based on your age, gender, medical history, the method used for testing, and other factors. The results may not mean you have a problem. To find out what they mean, talk to your healthcare provider.
The result of this test is generally expressed in seconds. The average clotting time is generally between 11 and 13 seconds. If your blood doesn’t clot within that normal range, you may have a bleeding or clotting disorder.
Suppose this test is done because you are taking a blood thinner, such as warfarin. In that case, the result is usually expressed as a number that compares your result to an expected value, known as the international normalized ratio (INR). . Healthcare providers generally look for the INR to be between 2.0 and 3.0 in people taking a blood thinner, such as warfarin.
How is this test done?
For the test, a blood sample is required. A needle is used to draw blood from a vein in the arm or hand.
Does this test involve any risks?
Taking a blood sample with a needle carries risks. These include bleeding, infection, bruising, or feeling dizzy. When your arm or hand is pricked with the needle, you may feel a slight stinging or pain. Afterward, the area may be sore.
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