Activated Partial Thromboplastin Time (APTT)

Edited by Joe Hing Kwok Chu This test is a modification of the Partial Thromboplastin Time (PTT).  PTT does not  contain added contact activator and is relatively insensitive to the effect of heparin.

APTT (activated partial thromboplastin time) is where PTT adds a contact activator to its reagent, thus activating factor XII (contact factor), and shortening the clotting time.

The APTT test is sensitive to heparin and evaluates all the clotting factors except factors VII and factor XIII.

Reference Range of Test: A fibrin clot forms 2.5 to 3.8 seconds after the reagent is added to the specimen.

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