Diseases of Platelet Number: Immune Thrombocytopenia, Neonatal Alloimmune Thrombocytopenia, and Posttransfusion Purpura

Chapter 56 Diseases of Platelet Number

Immune Thrombocytopenia, Neonatal Alloimmune Thrombocytopenia, and Posttransfusion Purpura

GP, Glycoprotein; HPA, human platelet antigen; RBC, red blood cell.

Terminology	Definition
ITP	Immune thrombocytopenia (rather than idiopathic or immune thrombocytopenic purpura)
Platelet threshold for ITP diagnosis	<100 × 10⁹/L
Primary ITP	ITP with no associated cause (diagnosis of exclusion)
Secondary ITP	ITP in the setting of an underlying cause such as drugs, HIV, or SLE
Newly diagnosed ITP	Designation for patients at diagnosis (rather than “acute” ITP).
Persistent ITP	Sustained or recurrent thrombocytopenia lasting 3-12 months
Chronic ITP	Thrombocytopenia lasting >12 months
Complete response	Achievement of a platelet count of ≥100 × 10⁹/L in the absence of bleeding
Response	Achievement of a platelet count of ≥30 × 10⁹/L and at least a twofold increase from baseline in the absence of bleeding
Refractory ITP	Failure to achieve a response or relapse after splenectomy* and requirement for treatment(s) to minimize the risk of clinically significant bleeding.