Performance characteristics of platelet autoantibody testing for the diagnosis of immune thrombocytopenia using strict clinical criteria

Br J Haematol. 2021 Jul;194(2):439-443. doi: 10.1111/bjh.17566. Epub 2021 Jun 9.


Misclassification of immune thrombocytopenia (ITP) is common, which might undermine the value of platelet autoantibody testing. We determined the sensitivity and specificity of platelet autoantibody testing using the direct antigen capture assay for anti-glycoprotein (GP) IIb/IIIa or anti-GPIbIX in patients with 'definite ITP', defined as those with a documented treatment response. Sensitivity of platelet autoantiboody testing increased from 48·3% [95% confidence interval (CI) 43·5-53·2] for all ITP patients to 64·7% (95% CI 54·6-73·9) for definite ITP patients. Specificity was unchanged [75·3% (95% CI 67·5-82·1)]. High optical density values (>0·8) improved the specificity of platelet autoantibody testing but lowered sensitivity. In patients with a high pretest probability, platelet autoantibodies can aid in the diagnosis of ITP and may be most prevalent in certain patient subsets.

Keywords: antibodies; platelets; purpura; registry; thrombocytopenia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Autoantibodies / immunology*
  • Blood Platelets / immunology*
  • Female
  • Humans
  • Immunoassay
  • Male
  • Middle Aged
  • Platelet Glycoprotein GPIIb-IIIa Complex / immunology
  • Platelet Glycoprotein GPIb-IX Complex / immunology
  • Purpura, Thrombocytopenic, Idiopathic / diagnosis
  • Purpura, Thrombocytopenic, Idiopathic / immunology*


  • Autoantibodies
  • Platelet Glycoprotein GPIIb-IIIa Complex
  • Platelet Glycoprotein GPIb-IX Complex