In-vitro diagnostics of adult immune thrombocytopenia - status quo and new developments

Adult immune thrombocytopenia (ITP) is an autoimmune disease characterized by low platelet count, purpura signs, and hemorrhagic episodes. ITP without a known underlying disease is referred to as primary ITP. Secondary forms are usually linked to identifiable causes, such as drugs or systemic autoimmune diseases. ITP is mediated by autoantibodies. These are directed against platelet membrane proteins, specifically glycoproteins (GPs). Antibody-coated platelets are cleared faster than usual by tissue macrophages, primarily in the spleen, shortening platelet half-life and resulting in thrombocytopenia. Additionally, T-cell-mediated cytotoxicity directed against bone marrow megakaryocytes leads to diminished platelet production. There are numerous specific diagnostic tests that assist in determining the underlying cause of thrombocytopenia and help to distinguish ITP from other disorders with similar clinical presentations. To confirm ITP, these tests rely on the identification of the underlying anti-platelet autoantibodies. The "monoclonal antibody immobilization of platelet antigens" (MAIPA) method, as the main exponent of these tests, is widely used in Europe. However, several additional assays are currently in use or under development and clinical validation. In general, assays for detecting anti-GP antibodies are characterized by high specificity but limited sensitivity. Their current role in the diagnostic evaluation of ITP, along with their advantages and limitations, are discussed in detail. This review gives an overview of the analytical techniques available and of the entire diagnostic evaluation of affected patients with primary or secondary ITP, including differential diagnostic considerations. In addition, it elucidates that personalized ITP treatment protocols require adequate laboratory diagnostic tests, which ensure treatment efficacy and safety.