A fast plasma reagin assay rpr test is a blood test used to screen you for syphilis. Reagent provided 1. Rpr carbon antigen suspension of carbon containing approximately 0. 003% cardio, Lipin, 0. 020% lecithin, 0. 09% cholesterol and 0. 2g/l charcoal in buffer and less than 0. 1% sodium azide as preservative. 2. Reactive control human serum containing antibodies against treponema pallidum and less than 0. 1% sodium azide as preservative. 3. Non, Reactive control human serum, Free of antibodies against treponema pallidum and containing less than 0. 1% sodium azide as preservative.