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Activated Partial Thromboplastin Time (APTT) - 000327

The activated partial thromboplastin time (APTT) is a test which is used to measure how long it takes for the formation of blood clots in your body. When there is an injury and bleeding occurs, our body reacts to bring a stop to this bleeding, which includes the activation of proteins called clotting factors which lead to the clumping of red cells to form a clot. If there is any disturbance to this normal process, then you may bleed for longer than normal.

An activated partial thromboplastin time measures the time taken for the formation of blood clots, and it gives your doctor an idea that you might be suffering from a bleeding disorder, which affects certain clotting factors, which form a part of the clotting cascade.

This test is usually done if your doctor suspects that you may be having a bleeding disorder and the process of clot formation is not occurring as it should in your body. This test is done to determine if there is an abnormality with a certain set of clotting factors which form a part of the clotting cascade. If you are taking anticoagulant medication such as heparin also you might have to undergo this test routinely.

There are no special preparations required before you undergo this test, but if you are on anti-coagulant medication, then you should get tested before you take your daily dose. Sometimes you may be requested to omit some of the blood thinning agents you are taking. Talk to your healthcare provider regarding this.

During this, a Medical Lab Technician will draw out a small volume of blood, using a needle and syringe which is inserted into a vein in your arm. This blood sample is then sent to the lab for analysis.

Since this test is a simple drawing of blood, you will not feel a lot of discomfort. You might experience a mild pain on inserting the needle, but you will not experience any uneasiness afterwards.

There is very little risk in undergoing an APTT test, because it is a simple blood drawing. But since this test is most often done on people with a bleeding disorder, there is an increased risk of excessive bleeding from the site of needle insertion. Very rarely you might continue to have a mild pain or some swelling and hematoma formation at the site where the needle was inserted, but these symptoms will resolve on their own within a couple of days.

Normal values for APTT should range between 30-40 seconds, if you are not on any anti-coagulants. For those on heparin, you can expect the time to be about 2 ½ times longer, ranging from 60-80 seconds. Results which are longer than this may indicate conditions such as bleeding disorders and liver disease. Results lower than this indicate that you have a higher risk of clot formation within your vessels.

Certain medication you may be taking such as aspirin and antihistamines may affect the results of this test. Therefore you have to bring all the medication you are taking to the notice of your doctor.