The magnitude of phagocytosis of platelets mediated by autoantibody-positive ITP serum related to the platelet count. The mean phagocytic index mediated for each ITP serum was explored for a potential relationship with the patient’s platelet count at the time of sera collection. All patients with ITP negative for MHC class I alloantibodies (19 total patients) were included in this analysis. (A) All ITP sera vs platelet count. (B) IgG autoantibody-positive ITP sera (any specificity by the indirect MAIPA) vs platelet counts. (C) IgG autoantibody-negative ITP sera vs platelet counts. The mean phagocytic index is shown for each patient. Data had a normal (Gaussian) distribution by the Shapiro-Wilk test and Pearson correlation coefficients were computed. A simple linear regression line for visualization is depicted.