The detection of antibodies to cytomegalovirus in the sera of renal transplant patients by an IgM antibody capture assay.

An IgM antibody capture assay for detection of cytomegalovirus (CMV) IgM antibody (MACRIA) was developed. It was shown to be of similar sensitivity to the indirect immunofluorescence test but has the advantage that rheumatoid factor does not react in it and pretest fractionation of serum is not required. It does, however, give false results with some Paul Bunnell-positive sera. The assay was used to measure the IgM response in 28 renal transplant patients followed prospectively. Seven patients (100%) with primary infections and six of 13 (46%) patients with secondary infections developed IgM by MACRIA. Nine of 13 (69%) patients with CMV IgM-positive sera had symptoms other than pyrexia associated with CMV infections, while only one of seven (14%) IgM-negative infections were symptomatic. Four of seven irreversible rejection episodes were associated with CMV IgM. The possible significance of CMV IgM production is discussed.