Detection of false seroconversions in cytomegalovirus seronegative platelet donors by serial complement fixation or IgG-specific radioimmunosorbent tests

A panel of 421 cytomegalovirus (CMV) seronegative-platelet donors was followed using complement-fixation (CFT) and IgG-specific radioimmunosorbent tests (RIST) to detect seroconversion. During 4623 person-months of observation 2452 serum specimens were tested, and the annual rate of seroreactivity detected by RIST was 56%. However, most of the positive RIST results were followed by negative results with later serum samples. CFT seroreactivity was a poor predictor of RIST seroreactivity. The high rate of transient seroreactivity detected by RIST may have reflected the lack of absolute specificity of the test. Alternatively, the results could illustrate the difficulty of determining whether an individual harbours latent CMV infection using antibody tests when some seronegative individuals appear to be latently infected. In the light of our observations recommendations for CMV antibody testing of blood donors are proposed.