The PT and INR blood test measures the time it takes your child’s blood to form a clot. Other names for the PT test are prothrombin time and pro time. INR stands for international normalized ratio.
The PT/INR test is usually done when your child is taking a blood thinner (anticoagulant) medicine, such as warfarin (Coumadin), to prevent blood clots. The test is done on a regular basis. Clots can block blood vessels and possibly cause a heart attack or stroke. This test measures the effect of the anticoagulant. If the dosage is too high, your child may bleed too easily and if it’s too low, your child’s blood may clot too easily. The test helps your child’s healthcare provider find the right dosage of medicine.
The PT test may also be done to diagnose a bleeding disorder if your child has abnormal or excessive bleeding or abnormal clotting.
Having this test will take just a few minutes. For young babies, the heel is pricked and a small amount of the blood is taken. For older children, a small amount of blood is taken from a vein in your child’s arm with a needle. The blood is collected in tubes and sent to a lab.
Ask your child’s healthcare provider when and how your child will get the results of the test.
A PT/INR value higher than normal means your child’s blood is taking longer than normal to form a clot. If your child is taking a blood thinner, it means that the medicine is working if the INR is in the goal range.
If your child is not taking a blood thinner and your child’s values are higher than normal, your child may:
Test results are only one part of a larger picture that takes into account your child’s medical history, physical exam, and current health. Sometimes a test needs to be repeated to check the first result. Talk to your child’s healthcare provider about the results and ask questions, such as: