RPR is used for the initial screening of patients for syphilis and to determine the efficacy of treatment.
Syphilis is a systemic, infectious disease caused by the spirochete Treponema (Treponema pallidum). The micro-organism is transmitted mainly through direct sexual intercourse and also through the placenta from mother to fetus. If syphilis is left untreated, infected people may develop irreversible complications such as chronic inflammation of the joints, cardiovascular problems such as valvular diseases and central nervous system problems such as mental illness and paralysis.
Laboratory diagnosis of syphilis can be made by direct and indirect tests. Direct tests include scraping off syphilis lesions and determining the causative organism. In indirect tests, they determine antibodies against Treponema. These antibodies do not appear in the serum until 3 to 4 weeks after the appearance of syphilis - an ulcer located at the point where the micro-organism first enters the body.
Serological testing for syphilis includes VDRL (Venereal Disease Research Laboratory), RPR (Rapid Plasma Reagin), TPHA (Treponema pallidum Haemagglutination Assay) and FTA-ABS (Fluorescent Treponemal Antibody-Absorbed Test) tests as well as IgM antibody screening, immunoenzymatic techniques (EIA). The VDRL and RPR are screening tests. Both of these tests have high rates of false-positive results. Conditions that can cause false-positive results include vaccination in children, antinuclear antibodies, blood loss (multiple transfusions), brucellosis, mild ulcer, chickenpox, cirrhosis, common cold, diabetes mellitus, fever, hypergammaglobulinemia, leprosy, leptospirosis (Weil's disease), Lyme disease, aphrodisiac lymphococci, lymphoma, infection (chronic), malaria, measles, infectious mononucleosis, mycoplasma pneumonia, non-mycoplasma pneumonia (bejel, pinta, yaws), periarteritis nodosa, pneumococcal pneumonia, pregnancy, rheumatic fever, rheumatoid arthritis, scarlet fever, scleroderma, aging, subacute bacterial endocarditis, systemic lupus erythematosus, tuberculosis (pulmonary advanced), trypanosomiasis, typhoid fever, vaccinia.
Due to the high rate of false positive results, any positive VDRL or RPR test should be followed by confirmatory testing, such as TPHA and FTA-ABS. These tests determine the specific antibodies against Treponema pallidum. The FTA-ABS test is the most sensitive test used to diagnose syphilis. This test will remain positive for life, even if the patient receives appropriate treatment.