The BioPlex 2200 Toxoplasma IgG assays uses multiplex flow immunoassay technology. Briefly, Toxoplasma antigen coated fluorescent beads are mixed with an aliquot of patient sample and sample diluent and incubated at 37 degrees C. During this time IgG anti-Toxoplasma antibodies in the specimen will bind to the Toxoplasma antigen on the beads. After a wash cycle, a fluorescently-labeled anti-human IgG antibody conjugate is added to the mixture and incubated at 37 degrees C. Following a wash step to remove unbound conjugate, the bead mixture is passed through a detector which identifies the bead based on dye fluorescence and determines the amount of antibody captured by the antigen based on fluorescence of the anti-human IgG conjugate. Raw data is calculated in relative fluorescence intensity and is converted to an Antibody Index for interpretation.
Three additional dyed beads, an internal standard bead, a serum verification bead, and a reagent black bead are present in each reaction mixture to verify detector response, the addition of serum to the reaction vessel and the absence of significant non-specific binding in serum, respectively.(Package insert: BioPlex 2200 System, ToRC IgG, Bio-Rad Laboratories, Clinical Diagnostics Group, Hercules, CA)