Rapid Plasma Reagin (RPR), Response to Therapy, Serum
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Syphilis is a disease caused by infection with the spirochete Treponema pallidum. The infection is systemic and the disease is characterized by periods of latency. These features, together with the fact that T pallidum cannot be isolated in culture, mean that serologic techniques play a major role in the diagnosis and follow-up of treatment for syphilis.
Patients with primary or secondary syphilis should be reexamined clinically and serologically 6 months and 12 months following treatment. Typically, rapid plasma reagin titers decrease following successful treatment, but this may occur over a period of months to years.
Determining the current disease status and evaluating response to therapy for syphilis
Treatment response is generally indicated by a 4-fold (2-tube dilution) reduction in rapid plasma reagin (RPR) titer (eg, from 1:32 to 1:8). For proper interpretation of RPR results, titers should be obtained using the same testing method and, preferably, at the same testing laboratory.
Failure of nontreponemal test titers to decline 4-fold within 6 months after therapy for primary or secondary syphilis may be indicative of treatment failure. Patients whose titers remain serofast should be reevaluated for HIV infection.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This test should not be used as a primary diagnostic approach for syphilis. For patients with suspected, undiagnosed syphilis, a serum specimen should be submitted for a treponemal-specific antibody test (eg, SYPGR / Syphilis IgG Antibody with Reflex, Serum).
This test cannot be used for testing spinal fluid specimens.
Biological false-positive reactions with cardiolipin-type antigens have been reported in disease such as infectious mononucleosis, leprosy, malaria, lupus erythematosus, vaccinia, and viral pneumonia. Pregnancy, autoimmune diseases, and narcotic addictions may give false-positives. Pinta, yaws, bejel, and other treponemal diseases may also produce false-positive results with this test.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Workowski KA, Berman S: Sexually transmitted diseases treatment guidelines. MMWR Morb Mortal Weekly Rep 2006 Aug 4;(55);22-30
2. Miller JN: Value and limitations of nontreponemal and treponemal tests in the laboratory diagnosis of syphilis. Clin Obstet Gynecol 1975 Mar 18;18(1);191-203