What is the Difference Between PT and PTT?

Prothrombin time (PT) and partial thromboplastin time (PTT) are tests used to evaluate coagulation, or the clotting of blood. They assess different pathways of the coagulation cascade:

• Prothrombin Time (PT): This test measures the integrity of the extrinsic system and factors common to both systems. It checks for different clotting factors than the PTT test. The PT test is often used to monitor patients taking certain medications and to help diagnose clotting disorders.
• Partial Thromboplastin Time (PTT): This test measures the integrity of the intrinsic system and the common components. It checks how well most of the clotting factors work. The PTT test is often ordered along with the PT test, and the results of both tests are compared to understand how the blood is clotting.

The main differences between PT and PTT are:

1. Pathways assessed: PT evaluates the extrinsic and common pathways of the coagulation cascade, while PTT assesses the intrinsic and common pathways.
2. Clotting factors measured: PT checks for different clotting factors than PTT. PT measures the integrity of the extrinsic system and factors common to both systems, while PTT measures the integrity of the intrinsic system and the common components.
3. Clinical applications: Both tests are used to evaluate coagulation disorders, but they are often used for different purposes. For example, PT is commonly used to monitor patients taking certain medications, while PTT is often used to find the cause of too much bruising or bleeding.

Comparative Table: PT vs PTT

PT (Prothrombin Time) and PTT (Partial Thromboplastin Time) are blood tests that measure the ability of the blood to form a clot and stop bleeding. Here is a table comparing the differences between PT and PTT:

Both tests together help doctors diagnose bleeding or clotting disorders and determine the reason for excessive bleeding or clotting problems.