To test your body's blood clotting abilities, the laboratory collects a sample of your blood in a vial and adds chemicals that will make your blood clot. The test measures how many seconds it takes for a clot to form. This test is sometimes called an activated partial thromboplastin time (APTT) test.

How long does an aPTT test take?

Usually, you get the results within a few hours or a day, but it depends on your lab. A typical value for a PTT is 60 to 70 seconds. There's also an activated PTT (aPTT) test that measures the same thing, but they add a substance to your blood to make it clot faster. A typical aPTT value is 30 to 40 seconds.

How coagulation test is done?

When a patient has an abnormally prolonged PT or aPTT, laboratories should perform a mixing study of the specimen (Table 1). To perform the test, the technologist mixes an equal volume of the patient's citrated plasma with normal pooled plasma (NPP) and repeats the PT and/or aPTT.