The goal of this study was to compare the BioPlex 2200 measles, mumps, rubella, and varicella-zoster virus (MMRV) IgG multiplex assays (Bio-Rad Laboratories, Hercules, CA) to routine testing by enzyme immunoassay (EIA). Serum specimens (n ؍ 500) submitted to our reference laboratory for routine MMRV IgG testing by EIA were also tested by the BioPlex assays. Following testing, the BioPlex measles, mumps, rubella, and varicella-zoster virus assays demonstrated agreements of 91.6% (95% confidence interval [CI], 88.8% to 93.7%), 94.2% (95% CI, 91.7% to 95.7%), 94.4% (95% CI, 92.0% to 96.1%), and 91.8% (95% CI, 89.0% to 93.9%), respectively, compared to the results of EIA. Timing studies showed that the BioPlex MMRV assay could provide complete analysis of 100 serum specimens in 1.7 h, compared to 5.5 h by EIA. These data indicate that the BioPlex MMRV IgG assays exhibit comparable performance (93% overall agreement [1,860/2,000 results];؍ 0.67) to routine testing by EIA. The BioPlex assays allow for the simultaneous detection of all four analytes, thereby eliminating potential aliquot errors and reducing turnaround time.The incidence of disease caused by measles, mumps, rubella, and varicella-zoster virus (MMRV) has been significantly reduced in developed countries due to the implementation of effective immunization programs (1, 6). However, outbreaks of disease continue to occur in the United States and worldwide due to vaccine failure, declining immunization rates, and waning immunity (2, 3, 5).Laboratory testing for IgG class antibodies to MMRV plays an important role in the management of patients and health care workers. For example, testing for IgG class antibodies to rubella virus is routinely performed during the prenatal period (7), and detection of rubella IgG during the first trimester indicates that the mother is protected from primary infection. Furthermore, immunocompromised hosts (e.g., transplant recipients) are commonly screened for immunity to varicella, which may cause devastating disease in the immunosuppressed population if a primary infection occurs (8).Until recently, most clinical laboratories have used methods such as indirect immunofluorescence (IFA), enzyme immunoassay (EIA), and enzyme-linked fluorescence assay (ELFA) for the detection of IgG class antibodies to MMRV. These methods have demonstrated reliable performance; however, they are labor-intensive, time-consuming, and, in the case of IFA, subjective. In addition, these conventional methods require four separate assays to test for IgG class antibodies to MMRV, thereby increasing sample volume requirements as well as hands-on time. These limitations have led to the recent development of multiplex flow immunoassay (MFI) technology, which allows for multiple analytes (e.g., antibodies) to be detected in a single reaction.The Bio-Rad BioPlex MMRV IgG assays (Bio-Rad Laboratories, Hercules, CA) recently received FDA approval for the simultaneous detection of IgG class antibodies to MMRV in human serum or EDTA/heparinized plasma sample...