Partial Thromboplastin Time, Activated
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To assist in assessing coagulation disorders and monitor the effectiveness of therapeutic interventions.
Plasma 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.
(Method: Clot detection) 25 to 35 sec. The aPTT is slightly prolonged in infants and children and is slightly shortened in older adults. Reference ranges vary with respect to the equipment and reagents used to perform the assay. For the patient on anticoagulants, therapeutic levels of heparin are achieved by adjusting the dosage so the aPTT value is 1.5 to 2.5 times the normal.