Evaluation of Cytomegelisa immunoglobulin M assay and comparison with indirect fluorescent antibody testing of QAE-Sephadex A50-treated sera.

The Cytomegelisa IgM assay (M. A. Bioproducts, Walkersville, MD) was evaluated as an alternative to indirect fluorescent antibody (IFA) testing of QAE-Sephadex A50-treated sera for detection of cytomegalovirus (CMV)-specific IgM. The Cytomegelisa assay was consistently more sensitive than IFA testing for detection of CMV-specific IgM. Of 101 rheumatoid factor-negative sera that were IFA positive before column separation, only 47 (46%) remained positive after column separation, while 72 (71%) were positive using Cytomegelisa. Nine transplant patients who had primary CMV infection develop were also evaluated. Two of the nine did not form sufficient IgM to remain IFA positive after column separation, however, all had IgM detected by Cytomegelisa. In all cases, Cytomegelisa provided laboratory evidence of CMV infection earlier or at the same time as IgG seroconversion or IgM testing by column/IFA. Comparison of both methods with 100 consecutive sera received for CMV testing yielded five sera positive for CMV-IgM with the column/IFA method and 20 using Cytomegelisa. The specificity of Cytomegelisa was evaluated with 56 RF-positive/CMV IgG-positive sera. Four of 56 (7%) appeared positive after column separation; however, of concern, 22 of 56 (39%) remained positive in the Cytomegelisa.