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Rapid Plasma Reagin Test

  • Detects antibodies to reagin: IgG and IgM antibodies directed against a lipoidal antigen resulting from interaction of T. pallidum and host tissues
  • Performed on unheated plasma or serum, not CSF
  • If antibodies are present, they combine with the lipid particles of the antigen, causing them to agglutinate.
  • The charcoal particles coagglutinate with the antibodies and show up as black clumps against the white card
  • #2, 3, 4, 6, 8, and 10 spots on the photograph of an RPR card are reactive and should be serially diluted and retested to report a titer
  • Rough looking reactions, such as #6, could indicate prozone effect
  • After dilution, if prozone is present, a strong reaction will be seen in higher dilutions