Partial Thromboplastin Time (PTT) Test

Partial Thromboplastin Time (PTT) is a medical test used to evaluate the clotting ability of blood. It measures the time it takes for the blood to form a clot in response to certain chemicals. PTT is usually ordered along with other coagulation tests like Prothrombin Time (PT) to diagnose bleeding or clotting disorders.

In this article, we will explore PTT in detail, including its uses, the procedure, and normal ranges. We’ll also answer some frequently asked questions about PTT.

What is Partial Thromboplastin Time (PTT)?

Partial Thromboplastin Time (PTT) is a laboratory test that measures the time it takes for the blood to clot after adding specific chemicals (reagents) that activate the clotting factors in the blood. PTT assesses the intrinsic pathway of coagulation, which includes factors VIII, IX, XI, and XII.

Why is PTT Performed?

PTT is usually ordered along with other coagulation tests to diagnose bleeding or clotting disorders. Some of the conditions that PTT can help diagnose include:

• Hemophilia A and B: Inherited bleeding disorders caused by deficiencies of factors VIII and IX, respectively.
• von Willebrand disease: A bleeding disorder caused by a deficiency or dysfunction of von Willebrand factor, which helps platelets stick to damaged blood vessels.
• Lupus anticoagulant syndrome: A condition in which the body produces antibodies that interfere with normal blood clotting.
• Liver disease: Impaired liver function can affect the production of clotting factors, leading to abnormal PTT results.
• DIC (Disseminated Intravascular Coagulation): A medical emergency where the clotting system is activated throughout the body, leading to both bleeding and clotting.

How is PTT Performed?

PTT is a simple blood test that can be performed in a clinical laboratory or hospital. The healthcare provider will usually draw blood from a vein in your arm and collect it in a tube. The blood sample is then mixed with the reagents, and the time it takes for the blood to clot is measured.

What Do PTT Results Mean?

The normal range for PTT varies slightly from one laboratory to another, but typically it falls between 25-35 seconds. If the PTT is longer than the reference range, it may indicate a bleeding disorder. If it’s shorter, it may indicate a clotting disorder.

It’s important to note that PTT results should always be interpreted in conjunction with other coagulation tests, medical history, and clinical findings.

Below is a table showing the normal PTT ranges for adults and children.