Simultaneous IgM reactivity by EIA against more than one virus in measles,parvovirus B19 and rubella infection

Background: A clinical diagnosis of rash-causing infections is not always p ossible and reliance has to be placed on serological evidence of infection, especially on the presence of specific immunoglobulin (Ig)M. However, desp ite the use of modern serological methods and validated commercial kits, re ports appear in the literature of simultaneous IgM reactivity against more than one virus in cases of Epstein Barr virus, rubella, cytomegalovirus, hu man parvovirus B19 (HPV B19) and measles infections, all with implications for the pregnant woman. Objectives: We decided to evaluate the extent of th e problem in rubella, measles and HPV B19 infections in a routine diagnosti c laboratory. Study design: We tested sera from cases with initial clinical and serological evidence of infection with measles, HPV B19 or rubella for evidence of simultaneous IgM reactivity against more than one virus. We co nfirmed primary infections with specific-IgG antibody avidity tests, and su bjected sera with IgM reactivity against more than one virus to avidity tes ts to identify which, if any, of the three viruses was the cause of the pri mary infection. Groups of monoreactive IgM sera were randomly selected from the presented sera to demonstrate that the avidity of the IgG specific for the other two viruses would be of high avidity compared with the low avidi ty of the IgG specific for the virus against which specific IgM had been de flected. Results: Our results confirm that simultaneous IgM reactivity agai nst more than one virus does occur in these three infections, and that this is unlikely to be caused by the presence of rheumatoid factor. Conclusions : In the absence of seroconversion, reliance on specific IgM results alone for diagnosis of these infections should be avoided and tests such as speci fic IgG antibody avidity should also be employed. The simultaneous occurren ce of IgM reactivity against more than one virus is also important for epid emiological and surveillance reasons as the widespread use of the mumps, me asles and rubella vaccine makes its impact on the population. Falsely diagn osed cases of apparent measles or rubella could throw into question the eff icacy of the vaccine. (C) 1999 Elsevier Science Ireland Ltd. All rights res erved.