Partial Thromboplastin Time (PTT) Test

The Partial Thromboplastin Time (PTT) test, also known as the Activated Partial Thromboplastin Time (aPTT), is a blood test used to evaluate the intrinsic and common coagulation pathways.

Purpose of the Test

The PTT test is used to:

• Assess the coagulation factors in the intrinsic pathway, including factors VIII, IX, XI, and XII.
• Evaluate the common coagulation pathway, which includes factors I, II, V, and X.
• Monitor patients on heparin therapy to ensure that their blood is not too prone to clotting or bleeding.
• Diagnose bleeding disorders, such as hemophilia A and B.

How the Test is Performed

The PTT test involves the following steps:

1. A blood sample is drawn from a vein in the arm or hand.
2. The blood sample is mixed with an anticoagulant to prevent clotting.
3. A chemical called activator is added to the blood sample to activate the intrinsic coagulation pathway.
4. The mixture is then incubated at a specific temperature for a set period of time.
5. The time it takes for the blood to clot is measured, which is known as the partial thromboplastin time.

Normal Results

A normal PTT result typically ranges from 25 to 35 seconds, but this can vary depending on the laboratory and the specific testing method used.

Abnormal Results

An abnormal PTT result may indicate:

• Prolonged clotting time: This can be caused by a deficiency or dysfunction of one or more coagulation factors, such as factor VIII or IX deficiency (hemophilia A or B), or the presence of an inhibitor.
• Shortened clotting time: This can be caused by the presence of a procoagulant substance or an increase in coagulation factors.

Clinical Significance

The PTT test is an important tool for diagnosing and monitoring bleeding disorders, as well as evaluating the effectiveness of heparin therapy. It can also help identify patients who are at risk of bleeding or thrombosis.

Frequently Asked Questions (FAQs)

What is a Partial Thromboplastin Time (PTT) test?
A blood test that measures the time it takes for blood to clot.

Why is a PTT test ordered?
To evaluate blood clotting, monitor heparin therapy, or diagnose bleeding disorders.

What is being measured in a PTT test?
The time it takes for plasma to clot after adding activators.

What are normal PTT test results?
Typically around 25-35 seconds, but may vary depending on laboratory and method.

What does a prolonged PTT result indicate?
May indicate a bleeding disorder, heparin effect, or other coagulation factor deficiencies.

How is a PTT test performed?
A blood sample is drawn from a vein, usually in the arm, and sent to a laboratory for analysis.

What factors can affect PTT test results?
Heparin therapy, warfarin, aspirin, and other medications, as well as liver disease and vitamin K deficiency.

Is a PTT test painful?
The blood draw may cause minor discomfort or bruising.

How long does it usually take to get PTT test results?
Typically several hours to a few days, depending on the laboratory and testing method.

What is the difference between PTT and PT tests?
PTT measures intrinsic clotting pathway, while PT measures extrinsic clotting pathway.