To evaluate the specificity and sensitivity of the microsphere-based multiplex fluorescent immunoassay (MFI) method for detecting antibodies in mice and rats naturally infected with MHV or SDAV/RCV, mouse and rat sera from a variety of sources submitted to the Central Institute for Experimental Animals for health screening were tested by MFI as well as ELISA and IFA for detection of anti-MHV or anti-SDAV/RCV antibodies.