Summary. Glycoprotein (GP)-specific platelet-associated IgG (PA-IgG) may be demonstrable in autoimmune-mediated thrombocytopenia. We studied 159 consecutive patients with histories of thrombocytopenia by a modified direct monoclonal antibody-specific immobilization of platelet antigens (direct MAIPA) assay, which immobilizes GP IIb/ IIIa, GP Ib/IX and GP Ia/IIa simultaneously. This modification requires smaller quantities of platelets than standard measurements performed separately. PA-IgG was present in 84/159 (53%) patients, as shown by the direct platelet immunofluorescence test (PIFT) with flow cytometry as a reference. PA-IgG against GP IIb/IIIa and/or GP Ib/IX and/or GP Ia/IIa was noted in 46 patients (29%), of whom 93% (43/46) were also PA-IgG positive. The amount of PA-IgG detected by PIFT correlated directly with that detected by direct MAIPA (r ¼ 0 . 71; P < 0 . 001). Only three patients 12548 with negative direct PIFT had GP-specific PA-IgG. GPV-specific PA-IgG was detected in 13 (10%) of the 125 patients, in whom further studies could be performed. In the subgroup of patients with GP-specific PA-IgG, the median fluorescence intensities of direct PIFT were higher than in patients with no GP-specific PA-IgG (P < 0 . 001). Direct PIFT and direct MAIPA divided the patients into asymmetric subgroups. However, the relative roles of these tests in the diagnosis of autoimmune-mediated thrombocytopenia await further studies.

To avoid unnecessary and possibly harmful monitoring and treatment, we need further tests for predicting the perinatal risks in pregnant women with ITP.

To avoid unnecessary and possibly harmful monitoring and treatment, we need further tests for predicting the perinatal risks in pregnant women with ITP.

Patients (n = 113) with histories of thrombocytopenia and with different profiles for platelet‐associated IgG (PA‐IgG) were subdivided according to the genetic polymorphism H131R in the Fcγ receptor type IIA (FcγRIIA). PA‐IgG was measured by the direct platelet immunofluorescence test (PIFT), and GP IIbIIIa and/or GP Ib‐specific PA‐IgG was investigated by a modified version of the direct monoclonal antibody‐specific immobilization of platelet antigens (MAIPA) assay. As a control, the distribution of FcγRIIA polymorphism H131R was determined among 93 healthy Finnish blood donors. The frequencies for H131 and R131 were 0.56 and 0.44 (CI: 0.37–0.51), respectively, which did not differ significantly from those in other Caucasian populations. The distribution of the genotypes HH131, HR131 and RR131 in the patients and controls did not differ significantly. In the HH131 group, the PA‐IgG was higher than in the RR131 group (p = 0.082). Female patients with the genotype RR131 seemed to be younger than those with HH131 (p = 0.065). Among the female patients, a significantly greater number were under 40 yr old in the RR131 group than in the HH131 group (p = 0.0060). Within the RR131 group, the female patients were far younger than the male patients (median 29 vs. 61 yr; p = 0.0021). The results point to the heterogeneity of immune thrombocytopenia, which may partly explain the poor predictive value of PA‐IgG studies.

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