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Rapid Plasma Reagin (RPR)
Principle
The RPR Card Test is a non-treponemal screening assay used for the serologic detection of syphilis. It is recommended when venous blood collection is performed. In this method, a carbon-particle cardiolipin antigen reacts with “reagin,” an antibody-like substance present in the serum of individuals with syphilis and occasionally in individuals with other acute or chronic conditions.
When reagin is present, visible flocculation occurs as the carbon particles in the RPR antigen coagulate, forming black clumps against a white background. Non-reactive specimens exhibit a uniform light gray appearance without clumping. Results are interpreted macroscopically.
Specimen Requirements
Specimen
Collect 2 mL of serum in a red-top tube (no anticoagulant).
Collection
Separate serum from cells as soon as possible to prevent hemolysis.
Storage and Transport
- 2–8 °C: use within 48 hours
- −80 °C: required if testing is delayed beyond 48 hours
Plasma
- Collect blood in EDTA anticoagulant tubes.
- Keep plasma in the original collection tube and centrifuge before use.
- Storage:
- 2–8 °C: use within 48 hours
Method
Agglutination Test.
Normal Range
Non-reactive
Turnaround Time
One Week
References
- Manual of test for syphilis, PHS Publication No. 411; 1969.
- Bender, et al. Clinical Laboratory Procedure Manual, NCCLS. Code GP2-A, Vol. 4, NO. 2.