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Laboratory Medicine

Test catalogue

Partial Thromboplastin Time, Activated (aPTT)

Test name

Partial Thromboplastin Time, Activated (aPTT)

Blue top Specimen Type / Requirements

Container Type = Blue

Minimum Volume = 9:1 Ratio – Full Draw

Specimen Handling

Collection Instructions: Collect blood into blue top vacutainers which contain 3.2% buffered sodium citrate. Must indicate anticoagulant status to avoid delay. NOTE: The ratio of blood to anticoagulant is 9 parts blood to 1 part anticoagulant, therefore the blue top vacutainer (citrate) must be filled AT LEAST ¾ in total volume.

Write your initials, date and time of collection on the collection label.

Stability: Stable frozen at -20C for up to two weeks or -70C for up to six months.

Transportation: Send sample to core lab as soon as possible. Specimens that cannot be tested within the suitable time frame (4hrs after Collection) are to be double-spun and send frozen.

Laboratory Staff Instructions: Centrifuge the blood sample at 4000 RPM (1500 G) for 8 minutes at room temperature (18-24˚C) on the Haematology robotics line centrifuge.

Sample Rejection Criteria:Clotted sample, Grossly hemolyzed samples, Unlabeled or Not Sufficient Quantity Samples will be rejected.

Required Documentation

Regular HIS order or Biochemistry requisition required.

Turnaround Time (TAT)

STAT:45min, Routine:4hrs

Test Utilization


Reference Value

24.0 - 37.0 seconds

Therapeutic range of heparin: 61.0 – 95.0 seconds

Test Code



Clot Based Assay

Testing Location

SMH-Routine Coagulation

Other Information

Last Updated: June 06, 2019