Autoimmunity Markers Prevalence Assessed in Immune Thrombocytopenia

Platelet autoantibodies in ITP lead to both acceleration of platelet destruction in the spleen and inhibition of platelet production by bone marrow megakaryocytes.

Although current guidelines recommend against routine testing of patients with ITP for autoimmune markers in the absence of disease-specific symptoms, there is general recognition that they frequently have autoantibodies associated with other autoimmune disorders in the absence of any clinical evidence of these disorders.

A number of studies have suggested that patients with ITP have a higher prevalence than the general population of positive autoimmune markers, including (ANA), rheumatoid factor (RF), anticardiolipin antibodies (ACL) immunoglobulin G (IgG) and immunoglobulin G (IgM), red blood cell direct antiglobulin test (DAT), antithyroid peroxidase antibodies (anti-ThyPeroxAb), and lupus anticoagulant (LAC).

Hematologists at Massachusetts General Hospital (Boston, MA, USA) and their colleague performed retrospective review of patients with ITP presenting to their center from 1 January 1992 to 1 December 2015. ANA assays were performed by indirect immunofluorescence assay, using Hep-2 cells (Zeus Scientific, Inc, Branchburg, NJ, USA). ThyPeroxAb assays were performed at Quest Diagnostics (Secaucus, NJ, USA) using an immunoassay method. RF markers were measured with an immunoturbidimetric assay on a cobas c 502 platform (Roche, Basel, Switzerland). Positive results for ACL were defined as >15 for IgG phospholipid units or IgM phospholipid (MPL) units. Glycoprotein-specific direct platelet autoantibody testing was performed with the PakAuto assay (Immucor, Brookfield, WI, USA).

The scientists reported that there was a high rate of autoimmune marker positivity in this population, with antinuclear antibody (65%), antithyroid peroxidase antibody (31%), and direct antiglobulin (29%) the most commonly found. Antithyroid peroxidase antibody positivity was associated with a lower probability of remission (odds ratio [OR], 0.26). Lupus anticoagulant positivity was associated with a higher rate of thrombosis (OR, 8.92), and antinuclear antibody was strongly associated with thrombosis. There was no relation between platelet autoantibody positivity and the presence of autoimmune markers.

The authors concluded that their results suggest that many patients with ITP have a state of immune dysregulation that extends beyond platelet autoantibodies and that certain autoimmune markers may be prognostically useful in this disorder. The study was published on November 15, 2019 in the journal Blood Advances.

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Massachusetts General Hospital
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