Detection of IgM antibodies specific for measles virus by capture and indirect enzyme immunoassays

During a measles outbreak, 112 serum specimens from 88 hospitalized patients were received in our laboratory for investigation of a morbilliform rash. These specimens (88 acute- and 24 convalescent-phase) were tested for the presence of measles-specific IgM antibodies by a capture EIA (enzyme immunoassay) using peroxidase-conjugated measles virus antigens and by an indirect EIA. Commercially available indirect EIA kits for measles-specific IgM antibodies were also used and compared with our homemade EIAs. Specificity studies included a collection of serum specimens containing rheumatoid factor, antinuclear antibodies or IgM antibodies specific to other viruses, and sera from blood donors and healthy children. Sensitivity of capture EIA and indirect EIA to detect measles IgM was 91.8 and 90.3%, respectively, and specificity was 98.2% for both tests. Specific IgM antibodies were detected in 70.5% of serum specimens at the first day after rash onset and were present for a month following the rash. Among the commercial measles IgM detection assays, EIA "Behring" was found to be a valid alternative for detection of measles virus-specific IgM.