Evaluation of Suspected HIT

Diagnosis of heparin-induced thrombocytopenia

(4T’s)

Thrombocytopenia

• ↓ >50% and nadir ≥20k
• ↓ 30–50% or nadir 10–19k
• ↓ <30% or nadir <10k

Timing

• 5–10 d or ≤1 d if heparin w/in 30 d
• ? 5–10 d (but not clear), >10 d or ≤1 d if hep w/in 30–100 d
• ≤4 d w/o recent hep

Thrombosis

• New thromb, skin necrosis, acute rxn after IV UFH
• Prog/recurrent thromb, suspect thromb or non-nec skin lesion
• None

OTher cause

• None apparent
• Possible
• Definite