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Test Code APTT Activated Partial Thromboplastin Time

Important Note

Specimen tube must be full. The ratio of blood to anticoagulant is critical. Incorrect blood to anticoagulant ratio will cause erroneous results.

Please indicate if patient is on anticoagulant therapy.

Specimen collected from patient receiving heparin therapy must be double centrifuged within 1 hr of collection and the plasma removed and frozen immediately.

Laboratory Code

LAB325

Specimen Requirements

Submit only one of the following specimens


Specimen Type: Whole Blood
Container/Tube: Light Blue Top (3.2% Sodium Citrate)
Volume: 2.7 mL Whole Blood (Tube must be full)

Collection Instructions:

1. Send whole blood specimen to laboratory immediately. APTT should be tested within 4 hours of collection.
2. If on heparin therapy, whole blood specimen must be centrifuged and tested within 1 hour of collection.
 

Specimen Type: Platelet Poor Plasma
Collection Container/Tube: Light Blue Top (3.2% Sodium Citrate)
Submission Container/Tube: Plastic Vial

Minimum Volume: 1.0 mL Plasma

Collection Instructions:
1. Light blue top tube must be properly filled with whole blood. Whole blood specimen should be double centrifuged and plasma separated from cells within 4 hrs of collection. If the testing is not completed within 4 hrs, the plasma should be kept frozen in well-closed plastic tube.
2. If on heparin therapy, whole blood specimen must be double centrifuged and plasma separated from cells within 1 hr of collection. Freeze the plasma in well-closed plastic tube immediately.

Specimen Stability

Specimen Type Whole Blood  (if NOT on heparin therapy) Plasma
Ambient 4 hrs (preferred) 4 hrs
Refrigerate Not available 4 hrs
Frozen Not available 14 days (preferred)

Methodology

Photo-optical Clot Detection

Days and Times Performed

24 hrs, TAT 1 day

Specimen Condition

Gross Haemolysis Reject
Icterus OK
Lipaemia OK
Others: Clotted or insufficient specimen Reject

Reference Interval

Adult 23.9 – 32.2 seconds

Critical value: > 100 seconds

Reflex Testing

  • APTT Mixing Study if the APTT is > 42.0 seconds

Testing Laboratory

National University Hospital
Haematology, 67725320

Useful For

Monitoring of heparin therapy. Screening test for intrinsic clotting factor deficiency (VIII, IX, XI, XII). Aids in detection of circulating coagulation inhibitors (e.g. Lupus anticoagulant).

APTT will be prolonged in disseminated intravascular coagulation, liver disease and vitamin K deficiency.

Service Code

12401

LOINC Code Information

APTT 14979-9
APTT(1+1) CORRECTION 5946-9
CONTROL PLASMA 13488-2

 

Alias

APTT
PTT
Partial Thromboplastin Time

Update

Last updated 21/03/2025