Heparin-induced thrombocytopenia differential diagnosis

Heparin-induced thrombocytopenia
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [2]

Overview

Heparin-induced thrombocytopenia is diagnosed when the platelet count falls by > 50% typically after 5-10 days of heparin therapy. It should be differentiated by other causes of thrombocytopenia like hemolytic uremic syndrome, Thrombotic thrombocytopenia and others.

Differential diagnosis

Diagnosis of Heparin-induced thrombocytopenia is mainly done with the help of lab tests. A decrease in platelet count by > 50% typically after 5-10 days of heparin therapy leads to a diagnosis of HIT. Thus, it should be differentiated from other causes of thrombocytopenia like

• Disseminated Intravascular Coagulation
• Thrombotic Thrombocytopenic Purpura
• Hemolytic-Uremic Syndrome
• Immune Thrombocytopenic Purpura
• Drug-Induced Thrombocytopenia
• Posttransfusion Thrombocytopenia
• Systemic Lupus Erythematosus

The table below summarizes the different findings between HIT and other diseases in the differential diagnosis:

Characteristic/Parameter	HIT	DIC	HUS	ITP	PTP	SLE
Symptoms	Bleeding, thrombosis, skin necrosis.	Bleeding, thrombosis, petechiae, sepsis.	Renal failure, hematuria, bleeding, microangiopathic hemolytic anemia.	Petechiae, bleeding, other autoimmune diseases.	Petechiae, purpura, ecchymoses.	Bleeding, photosensitivity, arthritis, malar rash, discoid rash, renal failure, seizures, psychosis.
Platelet count	Low but usually more than 20000 per microliter.	Low.	Low.	Low; can be as low as 10000 per microliter.	Low; can be less than 10000 per microliter; sudden onset after transfusion.	Variable; usually low.
PT and PTT	Normal.	Elevated.	Normal.	Normal.	Normal.	Usually normal.
Etiology	Heparin exposure.	Sepsis, delivery of fetus, acute promyelocytic leukemia, other malignancy.	E.coli strain O157:H7; Shiga-like toxin.	Idiopathic; can be secondary to chronic lymphocytic leukemia, HIV, viral hepatitis, H. pylori.	Exposure to transfused products.	Autoimmunity with development of antibodies to DNA.
Drug-related	Yes, always.	Possible.	No.	Yes.	No; transfusion-related.	Possible; drug-induced lupus can be caused by medications like hydralazine or isoniazid.
Bleeding	Possible.	Usually.	Usually.	Yes; spontaneous bleeding if platelet count < 10000 per microliter.	Yes; spontaneous bleeding if platelet count < 10000 per microliter.	Rare.

Table legend: HIT, heparin-induced thrombocytopenia; DIC, disseminated intravascular coagulation; HUS, hemolytic-uremic syndrome; ITP, immune thrombocytopenia purpura; PTP, post-transfusion purpura; SLE, systemic lupus erythematosis