Heparin-induced thrombocytopenia vs DIC
How to tell Heparin-induced thrombocytopenia and DIC apart when a board question makes them look alike.
HIT is heparin-timed platelet activation with thrombosis; DIC is systemic factor consumption with abnormal coagulation labs.
Side by side
Heparin exposure followed 5-10 days after first exposure, or hours after re-exposure, by platelet fall greater than 50%, new thrombosis, positive anti-PF4/heparin antibodies, and usually normal PT/PTT unless another process is present.
Systemic coagulation activation from sepsis, trauma, obstetric catastrophe, malignancy, or shock with bleeding, thrombosis, prolonged PT/PTT, low fibrinogen, high D-dimer, and thrombocytopenia.
IgG antibodies against heparin-PF4 complexes activate platelets, creating a paradoxically prothrombotic thrombocytopenia.
Widespread thrombin generation consumes platelets and clotting factors while fibrin breakdown raises D-dimer.
Post-heparin platelet fall, positive PF4 ELISA or serotonin release assay, thrombosis, and normal fibrinogen with normal PT/PTT support isolated HIT.
Prolonged PT/PTT, low fibrinogen, high D-dimer, schistocytes, and a systemic trigger support DIC.
The trap
Both have thrombocytopenia and thrombosis risk, so heparin timing and fibrinogen/PT/PTT decide the diagnosis.
Watch it explained
The repair move
For thrombocytopenia in the hospital, pair the timeline with coagulation-consumption labs.
Try a free question
CoreA patient started heparin after surgery. Five days later platelets fall by more than 50%, a new DVT appears, PF4 antibody testing is positive, and PT/PTT/fibrinogen are not consistent with factor consumption. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Heparin-induced thrombocytopenia. Heparin-timed thrombocytopenia with new thrombosis and PF4 antibodies points to HIT.
Why the other choices are tempting
- B. DIC should have factor-consumption labs such as prolonged PT/PTT and low fibrinogen.
- C. ITP causes isolated thrombocytopenia without heparin-timed thrombosis.
- D. TTP causes MAHA with normal coagulation tests but is not heparin-PF4 mediated.
- E. Vitamin K deficiency prolongs PT and later PTT rather than causing PF4-positive thrombosis.
Flashcards
Tap a card to flip it.
What timing points to HIT?
A platelet fall 5-10 days after first heparin exposure, or hours after re-exposure, points to HIT, especially with thrombosis.
Why is HIT prothrombotic despite low platelets?
Anti-PF4/heparin IgG activates platelets, driving thrombosis while platelets are consumed.
Quick answers
What is the fastest way to tell Heparin-induced thrombocytopenia from DIC?
HIT is heparin-timed platelet activation with thrombosis; DIC is systemic factor consumption with abnormal coagulation labs.
What is the key clue for Heparin-induced thrombocytopenia?
Heparin exposure followed 5-10 days after first exposure, or hours after re-exposure, by platelet fall greater than 50%, new thrombosis, positive anti-PF4/heparin antibodies, and usually normal PT/PTT unless another process is present.
What is the key clue for DIC?
Systemic coagulation activation from sepsis, trauma, obstetric catastrophe, malignancy, or shock with bleeding, thrombosis, prolonged PT/PTT, low fibrinogen, high D-dimer, and thrombocytopenia.
What is the common trap with Heparin-induced thrombocytopenia vs DIC?
Both have thrombocytopenia and thrombosis risk, so heparin timing and fibrinogen/PT/PTT decide the diagnosis.