Partial Thromboplastin Time (PTT) Test
A partial thromboplastin time (PTT) test uses a blood sample to measure the number of seconds it takes for your blood to clot .
A partial thromboplastin time (PTT) test uses a blood sample to measure the number of seconds it takes for your blood to clot . Normally, when you get a cut or injury that causes bleeding, many different types of proteins in your blood work together to make a clot to stop the bleeding. These proteins are called coagulation factors or clotting factors, and your liver makes most of them. If any of your clotting factors are missing, at a low level, or not working properly, your blood may: Clot too slowly after an injury or surgery. If this happens, you may have a bleeding disorder , such as hemophilia . These disorders can cause serious blood loss after an injury. Clot too much and/or too quickly, even without an injury. This may lead to unnecessary clots that block your blood flow and cause serious conditions, such as heart attack , stroke , or clots in the lungs . A PTT test helps check how many of a specific group of clotting factors you have and how well they’re working. If the blood in your sample takes longer than usual to clot, it may mean your body isn’t making enough of these clotting factors. To get a more complete understanding of your blood’s ability to make a clot, your health care provider may order other tests alongside a PTT test. The most common of these is called a prothrombin time (PT) test . A PT test measures other clotting factors that a PTT test doesn’t check. Your provider will usually compare the results of both tests to understand how your blood is clotting. Other names: activated partial thromboplastin time, aPTT, intrinsic pathway coagulation factor profile
Why is this test ordered? You may need a PTT test if you have: Problems with bleeding or bruising and the cause is not known. A blood clot in a vein or artery. Liver disease . This condition can affect your body’s ability to form blood clots. A history of several miscarriages , which can be caused by clotting issues. A bleeding or clotting disorder and don’t know which clotting factors are involved. Surgery scheduled and you have a history of excessive bleeding (including nose bleeds and easy bruising). Signs of an autoimmune condition that can cause clotting problems. Your provider may also order a PTT test if you’re taking heparin. With the results of this test, your provider will be able to ensure it’s a safe and effective dose. Lastly, your provider may order this test if you have symptoms suggesting a clotting disorder such as: Bleeding for a long time after minor cuts Joint pain or swelling Signs of excessive clotting such as pain, swelling, or warmth in your arms or legs
Clinical Interpretation
Your PTT test results will show how much time it took for your blood to clot. Results are usually given as a number of seconds. You may also see the results of a PT test alongside your PTT test results. In general, if your blood took longer than normal to clot on a PTT test , it may be a sign of: Hemophilia A or B. Liver disease. A lack of vitamin K . Certain genetic disorders that you inherit . That means that your parents passed the gene to you. These disorders affect certain clotting factors and increase your risk of bleeding. They include Von Willebrand disease and hemophilia. Too much heparin. Certain types of leukemia . Autoimmune diseases, such as lupus anticoagulant syndrome. Autoimmune diseases can affect your PTT test results by showing a slower clotting time than you actually have. That’s because the chemicals in the PTT test react with the autoantibodies in your blood sample. This reaction causes your blood sample to clot more slowly than the blood in your body. If your provider thinks that an autoimmune disease is causing a clotting problem, they will usually order more tests to make a diagnosis. If your blood clotted faster than normal on a PTT test , it may be a sign of: The early stage of disseminated intravascular coagulation (DIC). This rare but serious condition may develop if you have an infection or damage to organs or tissues that affects blood clotting. In the early stage, you have too much blood clotting. Later on, DIC starts to use up clotting factors in your blood, which leads to bleeding problems. High levels of clotting factors, such as during inflammation, pregnancy, or cancer. Cancer of the ovaries , colon , or pancreas that is advanced, which means the cancer has spread to other parts of the body and is unlikely to be controlled with treatment. Even if your sample clotted faster or slower than usual, that doesn’t necessarily mean you have a medical condition. This is because there can be a difference between how fast your blood clots in a test setting and how fast it clots in your body. Because of this, if your results are unusual, your provider may order more tests. Talk with your provider to learn what your test results mean for you. Learn more about laboratory tests, reference ranges, and understanding results .
Medicare Coverage — diagnoses supporting medical necessity (NCD)
Showing 18 of 6,284 diagnoses Medicare covers for this test under NCD 190.16. The complete list is in CMS's Lab NCD code list.
Clinical Protocol & Patient Advice
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You don't need any special preparations for a PTT test.
Usage Guidance
- Reference ranges vary by laboratory. Always discuss your specific results with a qualified healthcare professional.
Source: MedlinePlus, National Library of Medicine. View the original.
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