Partial thromboplastin time (PTT)

Definition

Partial thromboplastin time (PTT) is a blood test that measures the time it takes for blood to clot. It is used to evaluate the effectiveness of anticoagulant therapy, particularly heparin.

5 Must Know Facts For Your Next Test

1. PTT is primarily used to monitor patients on heparin therapy.
2. A prolonged PTT can indicate a clotting disorder or the presence of anticoagulant medications.
3. Normal PTT values typically range from 25 to 35 seconds, but this can vary depending on the laboratory.
4. PTT assessment helps in diagnosing conditions like hemophilia and von Willebrand disease.
5. The test involves adding calcium and a phospholipid reagent to a blood sample and measuring the time until clot formation.

Review Questions

• What is the primary use of Partial Thromboplastin Time (PTT) in clinical settings?
• How does PTT help in diagnosing clotting disorders?
• What are normal PTT values, and why might they vary between laboratories?

Related terms

Prothrombin Time (PT): A test that measures how long it takes blood to clot, commonly used to monitor warfarin therapy.

Heparin: An anticoagulant medication used to prevent and treat blood clots.

INR (International Normalized Ratio): A standardized number that's calculated based on PT results to monitor patients on warfarin.