Rickettsia ELISA modules are 12 x 8-well strip modules optimally coated with either lipopolysaccharide (LPS) antigens or outer-membrane (OmpA and OmpB) protein antigens. They are packaged in resealable pouches with 2 x 2 gram molecular seive desiccant packets. The LPS antigen is recommended for IgG testing, as this antigen is most often immunodominant and has broad reactivity for spotted fever organisms (SFG-96). The OmpA + OmpB antigen mix is more species-specific and is recommended for IgM testing, where they are the immunodominant antigens. Modules for IgG and IgM use are prepared with different antigens and coating concentrations and must be ordered separately.
Rickettsia IgM antibody can be accurately determined with our ELISA assay or by western blot assay, where the OmpA and/or OmpB antigens are the only useful markers. IFA and MIF assays may sound useful and are still the predominant clincal assays, but false-positives have been reported for many years. We looked at this annoying problem versus our ELISA assay for a poster presented at the 2018 American Society for Rickettsiology meeting in Milwaukee.