DEVELOPMENT AND EVALUATION OF CAPTURE ENZYME-LINKED IMMUNOSORBENT ASSAYS FOR DETECTION OF IMMUNO-GLOBULIN-G AND M ANTIBODIES TO GROUP-A STREPTOCOCCAL ANTIGENS

Capture enzyme-linked immunosorbent assays (ELISAs) were developed to detect immunoglobulin G and M antibodies to group A streptococcal (GAS ) antigens, streptolysin O, streptokinase, and group A carbohydrate. T he sensitivities and the specificities of the IgM capture ELISAs to ea ch GAS antigen were high enough to distinguish the patients with GAS i nfections (diagnosed as GAS pharyngitis or scarlet fever) from the con trol groups (healthy people and patients with pharyngitis from whom CA S could not be isolated). On the other hand, the specificities of the IgG capture ELISAs were not very effective in diagnosis of GAS infecti ons. When the capture ELISA and an indirect ELISA detecting IgM antibo dies to group A carbohydrate were compared, false-positive reactions d ue to rheumatoid factor occurred in the indirect ELISA, but did not oc cur in the capture ELISA. These results indicate that the capture ELIS A works better than the indirect ELISA in detecting the IgM antibody, and that the IgM capture ELISA to GAS antigen provides a rapid and hig hly reliable serodiagnosis for GAS infections employing only a single serum.