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Rapid Plasma Reagin (RPR)

Published: July 27, 2026Updated: August 25, 2026

The RPR test measures antibodies produced in response to syphilis infection, serving as a diagnostic tool for this infectious disease.

Quick summary

RPR is a blood test that detects syphilis antibodies, aiding in the diagnosis of the infection.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
titer
Clinical utility
diagnostic
Result kind
qualitative
FDA-cleared
Roche RPR, Siemens RPR, Abbott RPR
interpretation: {"text":"A titer of 0–1 indicates no active syphilis infection or successful treatment.","label":"Negative"}; {"text":"A titer above 1 suggests a possible active syphilis infection and requires further confirmation.","label":"Positive"}

The Rapid Plasma Reagin (RPR) test is a non-treponemal serological test used to screen for syphilis, an infectious disease caused by the bacterium Treponema pallidum. It detects the presence of antibodies, known as reagins, which are produced by the immune system in response to syphilis infection.

The RPR test is typically used as an initial screening tool due to its cost-effectiveness and ease of use. A positive result indicates the presence of syphilis antibodies, but it is not specific to syphilis alone and may be positive in other conditions. Therefore, a positive RPR test is usually followed by a more specific treponemal test for confirmation.

The RPR titer, expressed as a dilution ratio, helps monitor the course of the disease and the effectiveness of treatment. A declining titer indicates successful treatment, while a rising titer may suggest reinfection or treatment failure.

Frequently asked questions

What does a positive RPR test mean?
A positive RPR test indicates the presence of syphilis antibodies and suggests a possible active infection, but it is not definitive and requires confirmation with a more specific test.
Can the RPR test be used to monitor treatment?
Yes, the RPR titer can be used to monitor the effectiveness of treatment. A declining titer suggests successful treatment, while a rising titer may indicate reinfection or treatment failure.
  1. 1
    CDC - Syphilis - Diagnosis and TreatmentSource
  2. 2
    Mayo Clinic - Syphilis TestsSource

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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy