Test Code: Pf4Ab Preferred Name Heparin associated thrombocytopaenia

2 hours
As required
Medicare Item

Test Tubes

ImageSpecimen TypeSpecimen VolumeTube Type
Blood (adult)8.5 mlSST with gel 8.5 mL (Dark Yellow Top)
Blood (paediatric)600 ulSST with gel 600 uL Paed (Red or Yellow top)
Sodium Citrate 1.8 mL Paed (Clear/Pale Blue Inner)
Sodium Citrate 1.0 mL Neonate (Pale Blue Top)
Sodium Citrate 2.7 mL (Solid Pale Blue Top)


A dedicated SST or sodium citrate tube will be required for this test.
Accurate filling of sodium citrate tube essential.
Specimens must be transported at room temperature to the Laboratory in a red specimen bag ASAP. (Maximum delay to testing laboratory must not exceed 2hrs)
If difficulty collecting recommended amount please contactthe haematology laboratory on ext. 8500.


The hallmark of HIT is a fall in the platelet count between day 5 and 10 after starting heparin. A platelet count drop that exceeds 50% of a postoperative (high) value on day 1 of heparin treatment also strongly suggests HIT. Rapid platelet count falls may occur after previous exposure to heparin/LMWH. - The specificity of the anti-PF4/heparin ELISA is greatest when the OD value is > 1.0. The interpretation of a positive value between 0.4 and 1.0 is much less certain and is heavily dependent on clinical factors to determine if platelet-activating HIT antibodies are truly present. The incidence of false-positive ELISA results is highest in the 0.4-1.0 range and is due to non-pathogenic IgM and IgA antibodies or nonplatelet-activating antibodies.

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