Test Catalog

Test ID: RPRRT    
Rapid Plasma Reagin Screen Response to Therapy, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Determining the current disease status and evaluating response to therapy for syphilis


This test should not be used as a primary diagnostic approach for syphilis.


This test is not useful for testing spinal fluid specimens.


This test is not intended for medical-legal use.

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If this test is positive, then the titer will be performed at an additional charge.

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 (RPR) titers decrease following successful treatment, but this may occur over a period of months to years.


Treatment response is generally indicated by a 4-fold (2-tube dilution) reduction in RPR titer (eg, from 1:32 to 1:8). For proper interpretation of RPR results, titers should be obtained using the same testing method, 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.

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.


Interpretation Provides information to assist in interpretation of the test results


Specimen reflexed to determine rapid plasma reagin (RPR) titer value.



Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

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-positive results. Pinta, yaws, bejel, and other treponemal diseases may also produce false-positive results with this test.

Clinical Reference Recommendations for 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. doi: 10.1097/00003081-197503000-00017

3. Morshed M, Singh AE: Recent trends in the serologic diagnosis of syphilis. Clin Vaccine Immunol. 2015 Feb;22(2):137-147. doi: 10.1128/CVI.00681-14