Principles

The rapid plasma reagin (RPR) 18-mm circle card test is a macroscopic, non-treponemal flocculation card test. The RPR antigen detects anti-lipid antibodies (reagin) present in the serum or plasma of persons with syphilis. The antigen is prepared from a modified Venereal Disease Research Laboratory (VDRL) antigen suspension of serum, EDTA to enhance the stability of the suspension, and finally divided charcoal particles as a visualizing agent. For the test, the RPR antigen is mixed with serum or plasma on a plastic coated card. If antibodies are present, they combine with the lipid particles of the antigen causing them to agglutinate. The charcoal particles agglutinate with the antibodies and show up as black clumps against the white card. If no antibodies are present, the test mixture is uniformly gray.

_{Source: BD Macro-Vue RPR Package Insert}