Heparin induced thrombocytopenia (HIT) screen
|Category||Haematology >> Specialised Coagulation Services|
HIT with or without thrombosis (HITT) is mainly associated with treatment with unfractionated heparin (UFH), but it can also occur with low molecular weight heparin (LMWH). HIT is caused by the formation of abnormal antibodies that activate platelets, and may be suspected even if heparin treatment has already been discontinued, typically developing 4-14 days after the administration of heparin. Despite the low platelet count, it is a thrombotic disorder, with very high rates of thrombosis in the arteries, with or without venous complications. Of note, the rate of DVT is roughly 4 times that of arterial thrombosis and, while thrombocytopenia is the most common ‘event’ in HIT, DVT is in fact the most common complication. A commonly used score to predict the likelihood of HIT is the ‘4 Ts’ score, where: ≥6-8 is highly suggestive of HIT; 4-5 is intermediate probability and Thrombocytopenia: 2 points = a fall in platelet count of >50 %, or a lowest count (nadir) of 20-100×109/litre; 1 point = a fall of 30-50 % or a nadir of 10-19×109/litre; 0 points = a fall of less than 30 % or a nadir of 9/litre.
Discuss with laboratory before requesting.
|Sample & container required||Adults - 2.7 ml Sodium citrate (pale blue top) ; Paediatric – 1.8 ml sodium citrate (pale blue top)|
|Turnaround time||4 hours|
Special handling: avoid prolonged stasis during venepuncture. Sample must be received by lab within 4 hours of collection. Please note: samples will be rejected if underfilled or overfilled.