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Primary Immune Thrombocytopenia

Primary immune thrombocytopenia (ITP) is defined as a platelet count less than 100,000/uL in the absence of other causes or disorders that may be associated with thrombocytopenia. ITP is caused by the formation of autoantibody to an individuals’ own platelets that may also impair platelet production. Many patients are asymptomatic or only experience mild bruising or bleeding. Severe bleeding is uncommon with platelet counts greater than 30,000/uL. A small percentage of patients may develop serious bleeding complications when platelet counts fall below 10,000/uL.

In recent years, the diagnosis of ITP has been based on history, physical examination, CBC, peripheral smear exam, and exclusion of other causes of thrombocytopenia. This approach has been recommended by the American Society of Hematology, which stated that other diagnostic tests (including platelet antibody assays) are generally unnecessary, unless atypical findings are present suggesting other etiologies. Clinical utility of platelet antibody tests has remained controversial.

A prospective study analyzed the association between the presence or absence of platelet antibody and the clinical course of ITP. Fifty consecutive adult patients with ITP (both acute and chronic) were tested, using a modified ELISA assay for detection of serum autoantibodies against specific platelet glycoproteins (GP IIb/IIIa, GP Ib/IX, and GPIa/IIa). Fifty percent of the patients had detectable antibody and the other 50% did not. Patients were followed clinically for at least 6 months, and monitored for evidence of clinical worsening, defined as the need for starting or modifying therapy because of platelet counts lower than 10,000/uL, or admission for bleeding.

Antibody-negative patients had a significantly lower incidence of clinical worsening  (32%) compared with antibody-positive patients (72%). The median time to clinical worsening was 2.1 months for antibody-positive and 27.7 months for antibody-negative patients. Specificity of antibodies did not correlate with clinical outcome. In conclusion, this study provided evidence that the presence of platelet antibodies in patients with ITP may be a useful prognostic indicator.

Management of ITP is aimed at preventing clinically significant bleeding rather than normalizing the platelet count. A Choosing Wisely recommendation by The American Society of Hematology (ASH) is to not treat patients with ITP in the absence of bleeding or a very low platelet count. Specifically, ASH recommends treating patients with ITP who have platelet counts less than 30,000/uL or significant bleeding. In the absence of these criteria, observation is preferred.

Initial treatment options include corticosteroids and intravenous immunoglobulin. Response to steroids can take days to weeks. Intravenous immunoglobulin can be used when rapid improvement in platelet count is needed. Platelet transfusions should be reserved for emergency settings including life-threatening bleeding or need for emergent surgery. The benefit of platelet transfusions is only transient and increases the risk of alloimmunization. Second-line therapy includes splenectomy or medical management with immune modulators such as rituximab or thrombopoietin-receptor agonists.

A prospective studyof 245 adults diagnosed with ITP reported spontaneous remissions in 18% of patients, stable disease after treatment with steroids in 55% of patients, need for treatment with intravenous immunoglobulin or azathioprine in 19% of patients, and splenectomy in 12%.

In summary, patients with platelet counts greater than 30,000/uL and without significant bleeding can generally be safely monitored without ITP therapy. Unnecessary treatment should be avoided due to the risk of adverse effects in a population with an extremely low to no increased risk of bleeding.


Fabris F. et al. Platelet associated autoantibodies as detected by MACE are a useful prognostic factor in idiopathic thrombocytopenic purpura. Blood 2004;103(12)4562-4.

Neunert C. et al. The American Society of Hematology 2011 evidence-based practice guideline for immune thrombocytopenia. Blood 2011;117(16):4190-4207.

Neylon AJ et al. Northern Region Haematology Group. Clinically significant newly presenting autoimmune thrombocytopenic purpura in adults: a prospective study of a population-based cohort of 245 patients.  Br J Haematol 2003;122(6):966-74.

Wolfe HR et al. Treatment of immune thrombocytopenia. JAMA Internal Medicine, published online Dec 26,2017.

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