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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 hour of collection and the plasma removed and frozen immediately.

Specimen Requirements

Submit only one of the following specimens


Specimen Type: Whole Blood
Container/Tube: Light Blue Top (3.2% Sodium Citrate)
Volume: 2.7mL 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: 1.0mL 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 hours of collection. If the testing is not completed within 4 hours, 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 hour of collection. Freeze the plasma in well-closed plastic tube immediately.

Reference Interval

Adult 23.9 – 32.2 seconds

Call back values: Refer to Critical Values Table

Days and Times Performed

Monday through Sunday, TAT 1 day

Methodology

Photo-optical Clot Detection

Service Code

12401

Update

Last updated 23/05/2022

Unacceptable Condition

Haemolysis Gross reject
Icterus NA
Lipaemic NA
Others Clotted or insufficient reject

 

Specimen Stability

**Preferred temperatures for storage prior to and during shipping to NUH** 

 

Specimen Type

Whole Blood

(If NOT on heparin therapy)

 Plasma
Ambient Up to 4 hours 4 hours
Refrigerate NA 4 hours
Frozen NA 14 days

 

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.

Reflex Tests

  • APTT Mixing Study if the APTT is > 42.0 seconds

Alias

APTT
PTT
Partial Thromboplastin Time