Comparison of Four Serological Tests for the Detection of Specific Immunoglobulin M in Cord Sera of Infants Congenitally Infected with Cytomegalovirus

Four serological tests (3 immunoassays using enzyme-labelled antigen and 1 radioimmunoassay) were compared as regards the detection of cytomegalovirus (CMV) immunoglobulin M in cord sera. 68 cord sera from infants congenitally infected by CMV were included in the study. The infections were primarily diagnosed by virus isolation close to birth. Four laboratories in 3 countries were involved, each laboratory using its own or a commercial test. Of the sera tested in the different laboratories 50-80% were found to be reactive. Both qualitatively and quantitatively there was a good correlation between the 3 enzyme-immunoassays. The RIA results differed to some extent from the enzyme tests as regards the quantification of IgM. The advantage of prospective IgM screening in undiluted cord sera followed by confirmatory virus isolation test in the neonatal period in IgM-positive cases is discussed.