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Test ID RPRT1 Rapid Plasma Reagin (RPR) Screen with Reflex to Titer, Serum

Ordering Guidance

This test is for monitoring response to therapy in patients treated for syphilis infection. This test should not be used as a primary diagnostic approach for syphilis. To screen for undiagnosed syphilis infection, order SYPH1 / Syphilis IgG with Reflex, Enzyme Immunoassay, Serum

Specimen Required

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.

Useful For

Determining the current disease status


Monitoring response to therapy for syphilis


Aid to diagnose congenital syphilis


This test cannot be used for testing spinal fluid specimens.


This test is not intended for medical-legal use.


This assay provides a rapid plasma reagin (RPR) titer.

This test can be used to monitor response to therapy in patients treated for syphilis infection.

This assay can be used to help diagnose congenital syphilis when maternal and neonate sera are tested concurrently.

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
RPRT2 RPR Titer,S No No

Testing Algorithm

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

Method Name


Reporting Name

RPR Screen w/ Reflex to Titer,S

Specimen Type


Specimen Minimum Volume

0.4 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
  Frozen  14 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject

Clinical Information

Syphilis is caused by infection with the spirochete Treponema pallidum subspecies 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.


Historically, the serologic testing algorithm for syphilis included an initial nontreponemal screening test, such as the rapid plasma reagin (RPR) or the VDRL tests. Because these tests measure the host's immune response to nontreponemal antigens, they lack specificity. Therefore, a positive result by RPR or VDRL requires confirmation by a treponemal-specific test, such as the fluorescent treponemal antibody-absorption (FTA-ABS) or microhemagglutination (MHA-TP) assay. Although the FTA-ABS and MHA-TP assays are technically simple to perform, they are labor intensive and require subjective interpretation by testing personnel.


As an alternative to the traditional syphilis screening algorithm, many laboratories utilize the reverse syphilis screening algorithm. This algorithm starts with an automated treponemal assay to detect antibodies specific to T pallidum. If this screening assay is positive, the sample is reflexed for testing by RPR, which, if positive, is reported with a titer and is indicative of active or recent syphilis infection. If the RPR is negative, the sample is reflexed to a second treponemal assay, such as the T pallidum particle agglutination (TP-PA) assay. If the TP-PA is positive, this would indicate previously treated or late-stage syphilis infection. Alternatively, if the TP-PA is negative, the initial positive screen is interpreted as a false positive result.


Patients with primary or secondary syphilis are typically tested by RPR to monitor response to treatment. Typically, RPR titers decrease following successful treatment, but this may occur over a period of months to years. Additionally, testing of maternal and neonate serum, collected concurrently, by RPR can be used as an aid to diagnose congenital syphilis.

Reference Values


Reference values apply to all ages.



Nontreponemal antibodies not detected.


Specimen reflexed to determine rapid plasma reagin titer.


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, SYPH1 / Syphilis IgG with Reflex, Enzyme Immunoassay, Serum).


Biological false-positive reactions with cardiolipin-type antigens have been reported in diseases 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

1. Centers for Disease Control and Prevention (CDC): Discordant results from reverse sequence syphilis screening-five laboratories, United States, 2006-2010. MMWR Morb Mortal Wkly Rep. 2011 Feb;60(5):133-137

2. Radolf JD, Tramont EC, Salazar JC: Syphilis (Treponema pallidum). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Elsevier; 2020:2865-2892

3. Binnicker MJ, Jespersen DJ, Rollins LO: Direct comparison of the traditional and reverse syphilis screening algorithms in a population with a low prevalence of syphilis. J Clin Microbiol. 2012: Jan;50(1):148-150

Method Description

If the rapid plasma reagin (RPR) screen is reactive the RPR titer is performed. The RPR titer test is a macroscopic screening assay done with unheated serum. Reagin reacts with nontreponemal antigen containing colloidal charcoal particles. This reaction results in a visual flocculation of the black particles against the white card background. The test yields a positive or negative result, and all positive samples are titered to determine the highest positive dilution.(Huber TW, Storms S, Young P, et al: Reactivity of microhemagglutination, fluorescent treponemal antibody absorption, Venereal Disease Research Laboratory, and rapid plasma reagin tests in primary syphilis. J Clin Microbiol. 1983 Mar;17[3]:405-409; Kaur G, Kaur P: Syphilis testing in blood donors: an update. Blood Transfus. 2015 Apr;13[2]:197-204)

Day(s) Performed

Monday through Saturday

Report Available

Same day/1 to 4 days

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


86593-Rapid Plasma Reagin Titer (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
RPRT1 RPR Screen w/ Reflex to Titer,S 20507-0


Result ID Test Result Name Result LOINC Value
616863 RPR Screen w/ Reflex to Titer,S 20507-0


If not ordering electronically, complete, print, and send Infectious Disease Serology Test Request (T916) with the specimen.