Red-cell IgM-antibody capture assay for the detection of Mycoplasma pneumoniae-specific IgM

A red-cell IgM-antibody capture assay has been developed for detecting Mycoplasma pneumoniae-specific IgM, which is based on the adsorption or 'capture' of IgM from patients' sera onto so-called 'inagglutinable' bovine red cells, chemically linked with anti-human mu. When M. pneumoniae antigen is added to the system, the red cells agglutinate in the presence of M. pneumoniae-specific IgM. The test was compared with the mu-capture ELISA described by Wreghitt & Sillis (1985), and was found to give comparable results. The two tests had similar sensitivity and specificity and could detect M. pneumoniae-specific IgM for a similar time (up to 6 months) after proven M. pneumoniae infection. However, the red-cell antibody capture assay is a much more simple and rapid test, taking only 1 h to perform (compared to 24 h for mu-capture ELISA). The red-cell IgM-antibody capture assay is therefore amenable to rapid diagnosis of M. pneumoniae infection and the institution of early appropriate antibiotic therapy.