title: Is flow cytometry accurate enough to screen platelet autoantibodies?
abstract: BACKGROUND
  The diagnosis of immune thrombocytopenic purpura (ITP) is a diagnosis of exclusion, as stated by international guidelines. Nevertheless, the assessment of platelet (PLT) antibodies has been reported as helpful for the diagnosis and the follow-up of ITP patients. PLT antibodies are detected by highly specialized assays, such as monoclonal antibody-specific immobilization of PLT antigen (MAIPA) test. Flow cytometry for PLT-associated immunoglobulin G (PAIgG) detection has been described more recently. This study was meant to evaluate the utility of flow cytometry to screen accurately patients needing further MAIPA testing.
  
  
  METHODS
  PAIgG, PAIgM, and PAIgA were determined in 107 consecutive patients and in 147 healthy controls in parallel. MAIPA testing was performed in all patients. The accuracy of flow cytometry was assessed with a receiver operating characteristics (ROC) curve analysis versus MAIPA.
  
  
  RESULTS
  MAIPA assay found PLT-specific IgG in 27 patients (25%). The ROC curve analysis showed that no false-negative result in flow cytometry was obtained for a mean fluorescence intensity (MFI) cutoff of 0.2. With this cutoff, PAIgG were positive in 61 patients (57%). In this series, MAIPA was unnecessary in 42 percent of patients (corresponding to true-negative results). When MAIPA was positive, PAIgM values ranged from 0.1 to 1.0, and PAIgA from 0.1 to 2.
  
  
  CONCLUSIONS
  Flow cytometry for PAIgG assessment may be used to accurately decide whether or not MAIPA must be subsequently performed. In this series, MAIPA was unnecessary in 42 percent of patients. Moreover, PAIgM results suggested that its determination combined with PAIgG may be of interest in ITP investigation.
authors: Laboratoire d'Hématologie, CHU Robert Debré, Reims, France.
authors: Nathalie
authors: N
authors: Hézard
authors: Gérard
authors: G
authors: Simon
authors: Catherine
authors: C
authors: Macé
authors: Vincent
authors: V
authors: Jallu
authors: Cécile
authors: C
authors: Kaplan
authors: Philippe
authors: P
authors: Nguyen
mesh_terms: D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D001792:Blood Platelets / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results
chemical_list: D001323:Autoantibodies; D007074:Immunoglobulin G