Platelet-associated autoantibodies as detected by a solid-phase modified antigen capture ELISA test (MACE) are a useful prognostic factor in idiopathic thrombocytopenic purpura.

There were 50 consecutive idiopathic thrombocytopenic purpura (ITP) adult patients (platelet count < 100 x 10(9)/L) grouped according to positivity or negativity of a solid-phase modified antigen capture enzyme-linked immunosorbent assay (ELISA) test (MACE) against glycoprotein IIb/IIIa (GPIIb/IIIa), Ib/IX, and IIa/IIIa. Observation started on the day of MACE assay and lasted at least 6 months. Clinical worsening was defined as the need for starting or modifying therapy because of thrombocytopenia lower than 20 x 10(9)/L or patient admission due to bleeding symptoms. MACE-positive patients had a higher probability of clinical worsening than MACE-negatives (P <.004). The proportion of patients worsening was 18 (72%) of 25 among MACE-positives and 8 (32%) of 25 among MACE-negatives. The median time to clinical worsening was 2.1 months for MACE-positive patients and 27.7 months for MACE-negatives. The assay of specific platelet autoantibodies may be a useful prognostic tool for the clinical course of ITP.