Pathology Handbook

Antithrombin assay


AA, AT3, Antithrombin 3

Clinical Indications

Clinical / family history of thrombotic episodes

Please refer to Thrombophilia clinic or d/w Consultant haematologist BEFORE making request.

NOT available immediately post thrombosis or while patient on anticoagulant therapy.

It is strongly suggested to request a Thrombophilia screen rather than Antithrombin assay unless investigating a known low Antithrombin

Request Form 

Request via ICE


Mon - Fri 9AM to 4PM

Specific Criteria

Patient should be bled with minimal stasis

Patient Preparation

Patient should ideally be at rest and not in acute phase reaction

Turnaround Time

2 weeks


Fresh citrated Blood (within 2 hours of collection)


4.5 ml blue citrated blood


Blue capped vacutainer tube

Vacutainer blue top


Samples should be taken with minimal stasis and taken to the laboratory as soon as possible

Causes for Rejection

Underfilled, clotted or haemolysed samples

Reference Range

See patient test report