Synonym/Acronym:
aPTT, APTT.

Common Use:
To assist in assessing coagulation disorders and monitor the effectiveness of therapeutic interventions.

Specimen:
Plasma (1 mL) collected in a completely filled blue-top (3.2% sodium citrate) tube. If the patient’s hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted.

Normal Findings:
(Method: Clot detection) 25 to 35 sec. The aPTT is normally prolonged in infants, up to 55 sec, and gradually decreases to the adult range by age 6 mo. Reference ranges vary with respect to the equipment and reagents used to perform the assay.