Performance of eight commercial immunoassays for the detection of cytomegalovirus-specific IgM antibodies in pregnancy - no test fits all needs.

Detection of cytomegalovirus (CMV)-specific immunoglobulin M (IgM) antibodies as first-line serologic diagnosis plays an important role in identifying CMV primary infection during pregnancy. The performance characteristics of eight commercially available CMV IgM assays were compared. Sensitivity and IgM antibody kinetics were assessed using 100 acute phase and follow-up sera from 39 pregnant women with a well-defined onset of CMV primary infection. Specificity was analyzed using 50 well-characterized serum samples from pregnant women not infected or latently infected with CMV and from patients with other acute infections. Until 12 weeks after the onset of primary infection, four assays showed sensitivities of 100%, whereas the others had individual gaps to detect all primary infections in this time period. All assays showed a time-dependent decrease of IgM levels. More than 12 weeks after the onset of infection, the IgM-positive rates varied considerably between tests. The specificity was between 92% and 98% in all but one assay. The observed differences in the performance characteristics must be taken into account in CMV screening and diagnosis of primary infection during pregnancy.