What is the normal range for partial thromboplastin time (PTT)?

What is the normal range for partial thromboplastin time (PTT)?

• A. 10 to 20 seconds
• B. 20 to 30 seconds
• C. 25 to 35 seconds
• D. 40 to 60 seconds

Answer: (C)

The normal range for partial thromboplastin time is about 25 to 35 seconds. PTT measures the time for blood plasma to clot after activating the intrinsic and common coagulation pathways, so it reflects how well factors VIII, IX, XI, XII, and the common pathway are functioning. While exact numbers can vary slightly depending on the reagents and equipment a lab uses, 25–35 seconds is the standard reference range you’ll see in most labs. Values shorter than this are not typical of normal coagulation, and values longer than this suggest abnormalities such as coagulation factor deficiencies, inhibitors, liver disease, DIC, or the effect of anticoagulants like heparin. Therefore, 25–35 seconds is the best representation of a normal PTT.

The normal range for partial thromboplastin time is about 25 to 35 seconds. PTT measures the time for blood plasma to clot after activating the intrinsic and common coagulation pathways, so it reflects how well factors VIII, IX, XI, XII, and the common pathway are functioning. While exact numbers can vary slightly depending on the reagents and equipment a lab uses, 25–35 seconds is the standard reference range you’ll see in most labs. Values shorter than this are not typical of normal coagulation, and values longer than this suggest abnormalities such as coagulation factor deficiencies, inhibitors, liver disease, DIC, or the effect of anticoagulants like heparin. Therefore, 25–35 seconds is the best representation of a normal PTT.