The Activated Partial Thromboplastin Time test is a laboratory test used to measure how long it takes for your blood to clot. It measures the time it takes for a substance called “thromboplastin” to be added to a sample of your blood, causing it to coagulate into a solid form. Knowing how quickly your blood clots can provide information about various factors that influence this process in your body.

During an APTT Test, your healthcare provider will draw a small sample of blood from your arm or hand and send it off to a laboratory for analysis. In the lab, technicians will add thromboplastin, which causes the proteins in the blood sample to interact with each other and form a clot. The amount of time it takes for the clotting process to occur—from the moment thromboplastin is added until all proteins form into a solid mass—is measured precisely using special equipment. This measurement is then compared against normal values to determine whether there are any abnormalities present within your results.

In some cases, there may be risks associated with taking an APTT Test such as slight discomfort during blood collection or possible allergic reactions due to contact with substances used in testing procedures. That said, these risks are rare and typically very minor when compared to the potential benefits of knowing one's risk factors related to clotting disorders. If there is any concern about potential risks involved in taking this test, discuss them openly with your doctor before proceeding with scheduling an appointment for the procedure itself.

One potential cause of elevated aPTT levels is the use of certain medications. Certain anticoagulants such as warfarin (Coumadin), heparin, and low-molecular-weight heparins may increase your risk for an abnormally high aPTT result. Other drugs that may contribute to elevated levels include aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and immunosuppressive medications. Additionally, genetic factors such as deficiencies in certain clotting factors can also lead to abnormal aPTT results.