Immune Thrombocytopenia and Pregnancy Workup

Updated: Aug 19, 2019
  • Author: Muhammad A Mir, MD, FACP; Chief Editor: Srikanth Nagalla, MBBS, MS, FACP  more...
  • Print

Laboratory Studies

No laboratory test can differentiate immune thrombocytopenic purpura (ITP) from other causes of maternal thrombocytopenia. Therefore, the diagnosis of ITP is based on a personal history of bleeding, a low platelet count prior to pregnancy, and/or a family history that excludes hereditary thrombocytopenia (HT). [4]  Platelet counts less than 70,000/µL are suspicious for the disorder if no other etiology for thrombocytopenia is identified. [22]

Bone marrow aspiration demonstrates normal or increased numbers of megakaryocytes. Guidelines from the American Society of Hematology state that a bone marrow examination is not required in adults younger than 60 years who have a classic presentation for ITP. However, the bone marrow should be assessed prior to proceeding with splenectomy.

Antiplatelet antibodies can be detected in the serum of women with ITP. The direct assay for the measurement of platelet-bound autoantibodies has an estimated sensitivity of 49-66% and an estimated specificity of 78-92%. A negative test does not exclude the diagnosis. [23] Additionally, many women with gestational thrombocytopenia have high levels of circulating platelet-associated immunoglobulin. Therefore, current antiplatelet antibody assays cannot be used to differentiate between ITP and gestational thrombocytopenia.

In newborns, a platelet count less than 150,000/µL is consistent with thrombocytopenia. Consider neonatal alloimmune thrombocytopenia (NAIT) in the differential diagnosis of any significantly thrombocytopenic newborn (platelet count <  50,000/µL) or in newborns with intracranial hemorrhages (platelet count <  100,000/µL) in whom other illnesses commonly associated with thrombocytopenia have been excluded, as follows [19] :

  • Platelet antigen typing can determine the genotype of the mother and father of the baby to determine if they are discordant.

  • Test the maternal sera for the presence of a platelet antibody that binds paternal, but not maternal, platelets.

  • A lack of antiplatelet antibody does not exclude the diagnosis of NAIT because, in a number of cases, no antiplatelet antibody could be detected when fetuses were profoundly thrombocytopenic due to NAIT. [9]

Other laboratory tests are as follows:

  • Complete blood cell count (CBC) with differential
  • Peripheral blood smear
  • Thyroid-stimulating hormone (TSH)
  • Prothrombin time/activated partial thromboplastin time (PT/aPTT)
  • Liver function tests
  • Hepatitis B and C and HIV serologies
  • Antinuclear antibody
  • Antiphospholipid antibodies