What is a Rapid Plasma Reagin (RPR) lab test?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: April 14, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

An RPR lab, or Rapid Plasma Reagin test, is a blood screening test used primarily to detect syphilis infection. This test works by identifying antibodies that the body produces in response to the bacterium Treponema pallidum, which causes syphilis. RPR is considered a non-treponemal test that measures the body's response to substances released during cellular damage caused by the infection rather than detecting the bacterium directly. The test is typically ordered when a patient shows symptoms of syphilis, has been exposed to someone with syphilis, or as part of routine prenatal or STI screening. Results are usually reported as reactive (positive) or non-reactive (negative), often with a titer value if positive that indicates the concentration of antibodies. While RPR is sensitive for detecting syphilis, it can produce false-positive results due to other conditions like autoimmune diseases, pregnancy, or other infections. Therefore, a positive RPR test is usually followed by a more specific treponemal test to confirm the diagnosis of syphilis, as recommended by the US Preventive Services Task Force 1.

Some key points to consider when interpreting RPR test results include:

  • The test is most sensitive in the early stages of syphilis infection 1
  • False-positive results can occur due to other conditions, so confirmation with a treponemal test is necessary 1
  • The test is an important tool for screening high-risk populations, such as pregnant women and individuals with a history of sexually transmitted infections 1

Overall, the RPR test is a valuable tool for detecting syphilis infection, but it should be used in conjunction with other diagnostic tests and clinical evaluation to confirm the diagnosis and guide treatment.

From the Research

Definition of RPR Lab

  • RPR lab refers to a laboratory test used to diagnose and monitor syphilis, a chronic and multi-stage infectious disease 2.
  • The test measures the level of antibodies in the blood against the syphilis bacteria, Treponema pallidum, and is used to assess disease activity 3.

How RPR Lab Works

  • The RPR (Rapid Plasma Reagin) test is a non-treponemal test that detects the presence of antibodies in the blood that are produced in response to a syphilis infection 3.
  • The test involves taking a blood sample and measuring the level of antibodies against the syphilis bacteria 4.
  • The results of the RPR test are reported as a titer, which indicates the level of antibodies in the blood 4.

Uses of RPR Lab

  • The RPR test is used to diagnose syphilis, particularly in its early stages 2.
  • It is also used to monitor the effectiveness of treatment for syphilis, as the level of antibodies in the blood should decrease after successful treatment 4, 5.
  • The RPR test can also be used to diagnose neurosyphilis, a complication of syphilis that affects the central nervous system 6, 5.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Syphilis: antibiotic treatment and resistance.

Epidemiology and infection, 2015

Research

The Laboratory Diagnosis of Syphilis.

Journal of clinical microbiology, 2021

Research

Management of adult syphilis.

Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 2011

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.