<prompt> The RPR test uses VDRL antigen containing fineCarbon paiclesIodine paiclesSilver ionsSodium ions  <response>: The rapid plasma reagin RPR test is a macroscopic, nontreponemal flocculation card test used to screen for syphilis. RPR antigen is prepared from a modified VDR antigen suspension containing choline chloride to eliminate the need to heat inactivate serum, ethylenediaminetetraacetic acid EDTA to enhance the stability of the suspension, and finely divided charcoal paicles as a visualizing agent. Ref: Ananthanarayana textbook of Microbiology 9th edition Pgno : 374 