SERUM PLATELET ANTIBODY TESTING - EVALUATION OF SOLID-PHASE ENZYME-IMMUNOASSAY AND COMPARISON WITH INDIRECT IMMUNOFLUORESCENCE

We compared the ability of solid-phase enzyme immunoassay (SPEIA) with that of indirect immunofluorescence to detect serum platelet antibodi es by parallel testing five sets of serum specimens: (1) 12 monospecif ic HLA class I specimens with defined specificities, (2) 4 HPA-1a spec imens, (3) 164 sequential unselected specimens sent to our laboratory for serum platelet antibody testing, (4) specimens from 15 consecutive patients sent for indirect immunofluorescence testing alone, and (5) specimens from 19 consecutive patients sent for both indirect and dire ct immunofluorescence testing. In addition, specimens of HLA sera were tested by standard complement-dependent lymphocytotoxicity. Solid-pha se enzyme immunoassay was consistently more sensitive than indirect im munofluorescence for all 12 HLA specimens and more sensitive than comp lement-dependent lymphocytotoxicity for 11 of 12 specimens. Similarly, SPEIA was more sensitive than indirect immunofluorescence for all fou r HPA-1a serum specimens by one to three dilutions. In the nine presum ed autoimmune cases (group 5), results were positive with SPEIA in one case; no positive results were noted with indirect immunofluorescence . The solid-phase enzyme immunoassay test permits ready differentiatio n between alloantibodies directed to HLA and those directed to platele t-specific glycoproteins.