Evaluation of a commercial assay for the detection of mumps specific IgM antibodies in oral fluid and serum specimens

An IgM antibody capture radioimmunoassay (MACRIA) has been used in the UK Reference Laboratory for the detection of mumps specific IgM antibodies in oral fluid and serum samples. The method has proved both sensitive and specific and has been used for the surveillance of mumps since 1994. The use of radioactive labels has restricted the use of MACRIA to specialised laboratories and alternative, non-isotopic, sensitive assays capable of detecting the low levels of specific antibodies in oral fluid have not been available. Recently, a novel mumps specific IgM capture enzyme immunoassay (MACEIA) utilising recombinant mumps nucleoprotein (rMuVN) and monoclonal antibodies to the nucleoprotein, produced by Microimmune Limited, has been developed for use with both serum and oral fluid samples. In this study, we have evaluated the performance of the Microimmune MACEIA for both serum and oral fluid against specimens tested by MACRIA. The panel consisted of matched serum and oral fluid specimens from 137 cases of suspected mumps received in the Virus Reference Department for routine investigation from March 2003 to October 2004. The sensitivity, specificity, positive and negative predictive value of the Microimmune MACEIA on serum samples compared to MACRIA were 98.8%, 100.0%, 100.0% and 98.5%, respectively. The sensitivity, specificity, positive and negative predictive value of the Microimmune MACEIA on oral fluid samples compared to Microimmune MACEIA and MACRIA consensus results on the paired serum samples were 90.3%, 97.6%, 98.3% and 87.1%, respectively. The Microimmune MACEIA was found to be a rapid, sensitive and specific alternative to MACRIA for the detection of mumps specific IgM in sera and oral fluids.