Detection of drug-dependent antibodies. (A) Platelet count evolution. (B) Monoclonal antibody-specific immobilization of platelet anti-gene (MAIPA). Platelet antibodies were characterized using CD41 antibodies to immobilize the platelet GpIIb/IIIa. Human platelet antibodies were detected by a peroxidase-conjugated goat anti–human IgG Fcγ fragment. Optical density (OD) at 492 nm was considered negative at less than 0.2 OD units. Negative controls comprised group AB serum and the drug diluent (saline serum). Human polyclonal sera containing anti–HPA-1a, anti–HPA-5b or anti-GpIb/IX activity served as positive controls. S1 volume was insufficient for MAIPA. In assays, drugs were added to incubation and wash solutions at final concentrations of 0.05, 0.1, and 0.2 mg/mL MP, and 0.002, 0.004 and 0.008 mg/mL dexamethasone (DXM). S1, S2, and S3 serum samples. DXM indicates dexamethasone; MP, methylprednisolone; IgIV, intravenous immunoglobulins; and Pdn, prednisolone.