Days Set Up
Daily, 24 hours
Analytic Time

STAT 1 hour, Routine 4 hours

MiChart Code
Soft Order Code

Test Updated:


Activated Partial Thromboplastin Time

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Test Overview

Test Methodology

Photo-optical clot determination

Test Usage

Evaluation of intrinsic coagulation system, aid in screening for presence of classical hemophilia A and B, Christmas disease, congenital deficiencies of factors II, V, VIII, IX, X, XI and XII, dysfibrinogenemia, disseminated intravascular coagulation, liver failure, congenital hypofibrinogenemia, vitamin K deficiency, congenital deficiency of Fitzgerald factor and prekallikrein.

Reference Range

22 - 29 seconds. If the aPTT is being used to monitor heparin, the current applicable heparin nomogram should be used.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Specimen Requirements

Collection Instructions

Collect specimen in a blue top (citrate 3.2%) tube. Mix by inversion. Specimen should arrive at lab within 3 hours of collection; transport at room temperature. Alternatively, centrifuge, aliquot plasma into a plastic tube, and freeze the specimen within 4 hours of collection. Transport frozen specimen on dry ice. Collection of the blood through lines that have been previously flushed with heparin should be avoided. If the blood must be drawn through a VAD (vascular access device), the line should be flushed with 5 mL of saline and the first 5 mL of blood or six dead space volumes of the VAD discarded.

Blue Top Tube
Normal Volume
Full 2.7mL tube or 1mL plasma aliquot
Minimum Volume
Full 1.8mL tube or 1mL plasma aliquot

Billing Information

CPT Code
Pro Fee Code
Insurance Auth Info

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Our High Standard

Quality that sets us apart

As the reference laboratory division of Michigan Medicine's Department of Pathology, MLabs shares the institution's commitment to applying established quality principles to clinical laboratory testing. Like other large organizations in complex, consequential fields, we rely on an established approach to monitor quality throughout the testing process.