RPR (Rapid Plasma Reagin) Card Test For Syphilis

This test is based on the relationship between the lipid extract of tissue i.e. cardiolipin-cholesterollecithin. These lipids act as antigen against a non-specific antibody (reagin) which develops in the blood serum of syphilis affected persons. RPR is useful as a rapid screening test for syphilis patients. In this test only small amount of serum or plasma is used . Prior inactivation of serum or dilution of antigen is not required.

RPR is similar to VDRL except that in RPR blood serum of a patient is mixed with soluble reagin antigen bound to carbon particles within a circle on the diagnostic card. Due to carbon coating visual differences between positive and negative result are enhanced.


  • Applicator sticks
  • Capillary pipette
  • Non-syphilis serum
  • Serum/plasma from syphilis patient
  • RPR test kit
  • Saline


  1. Take a diagnostic card (made up of plastic) from the RPR kit and label the circles as reactive and non-reactive ones.
  2. With the help of a capillary pipette, drop 0.5 ml of reactive serum in one of the labelled
  3. reactive circles and spread the serum with a clean applicator stick.
  4. Similarly, drop 0.5 ml reactive serum in one of the labelled non-reactive circles and spread the serum in circle as above.
  5. Add 1 drop of antigen suspension onto each circle containing test serum and shake it thoroughly.
  6. Rotate the card on a rotor at 100 rpm or manually rotate back and forth for about 10 minutes.


By tilting the card all round, observe the presence/absence of black clumping in the mixture of serum and antigen. Observe the same under microscope. Black agglutination reaction is the indication for positive test of syphilis and light grey for negative test.


Dr. R. C. Dubey – Practical Microbiology

Gaurav Singh

Editor in Chief Medical Microbiology & Recombinant DNA Technology (RDT) Labs - RDT Labs Magazine

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