Blood test that measures the time, in seconds, it takes for activation of the extrinsic coagulation cascade. It is commonly referred to as “Pro Time.”
The approximate range for PT is 10-14 seconds. The higher the number, the longer it takes for the blood to clot.
Activated Partial Thromboplastin Time (PTT or aPTT) evaluates the intrinsic and common pathways of the coagulation cascade. aPTT is used to measure the therapeutic effects of Heparin, which prevents clotting by blocking certain factors in the intrinsic pathway.
The value of aPTT also depends on the reagents and instruments used. The normal range is between 25-35 seconds. The aPTT is monitored closely for patients on Heparin drips in the hospital.
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