Q: How lupus and antiphospholipid syndrome (APS) can be differentiated from Heparin Induced Thrombocytopenia (HIT)?


Answer: 

1. Lupus usually causes only mild thrombocytopenia and  almost never drops platelet count below  50,000/microL. Moreover, lupus-associated antiplatelet antibodies do not activate platelets and do not cause thrombosis.

2. APS,  like HIT can cause arterial and venous thrombosis but can be differentiated  from HIT

• by interaction of APS antibodies with phospholipids i.e cardiolipin and ß2-GP-I
• prolongation of the aPTT
• Platelet count almost never dropping below 50,000/microL