PTD - 33

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Test Directory -  Heparin Induced Thrombocytopaemia


HIT Test

Clinical Indications

Patients receiving heparin with falling platelet count

Test Includes

Screening for antibodies against the heparin/platelet Factor 4 complex.

Request Form

Combined Pathology Blood form (Yellow/Black or Blue for GP's). Please send a completed ‘4Ts’ Pre Test Scoring System for HIT form (click here)


On request when accompanied by completed 4T assessment form. Please contact the haematology laboratory, sample must be received within 2 hours of collection.

Specific Criteria

Discussed and agreed with Consultant Haematologist.

Turnaround Time

Screen result available within 4 hours of receipt. If screen is positive, samples are sent for confirmation to Reference laboratory (24hours to 1 week).


Serum & Whole blood (Citrate)


 12 mL serum & 6 ml citrated whole blood


2 x Red Top (Plain) tube (minimum 1 sample), 2 x Citrated (Blue top)


Sample must be received by lab within 2 hours of collection.

Lab. Handling

Processed on receipt. save serum samples as instructed in SOP. Samples testing positive are sent to referral laboratory for confirmatory testing.

Causes for Rejection

Inadequately labelled, unlabelled, haemolysed, or lipaemic samples. Sample received more than 2 hours after collection.

Reference Range

This test screens for the presence of HIT antibodies. Interpretation as to the clinical likelihood of HIT should only be made in conjunction with a decreased platelet count and the clinical signs and symptoms observed in the patient. (see the 4Ts score form)



Version 1.0 / January 2013