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STDWatch
Dr. Patricia Shelton

Dec 02, 20227 min read

RPR Test: Purpose, Procedure, and Results

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Syphilis is a common sexually transmitted disease, and the rates of this disease have been increasing in recent years. It can be spread through many types of sexual contact, including anal, vaginal, or oral sex. If it’s caught early, syphilis can almost always be treated with antibiotics. However, if the disease goes untreated, then the bacteria can cause permanent damage to the brain and other parts of the body.

When you’re looking at your STD test results, you may see “RPR” on the list. Many people start wondering, “What is the RPR meaning in medical terms? What does RPR test for?”

What is RPR in a blood test?

RPR stands for Rapid Plasma Reagin. This is a test that looks for certain types of antibodies in the blood. Antibodies are made by the body in response to an infection. The RPR test looks for antibodies against Treponema pallidum, which is the bacteria that causes syphilis. 

The RPR test for syphilis is generally used as a screening test. By itself, it’s not enough to definitively diagnose syphilis. Instead, it’s used to screen people who may be at risk. If the test is positive, further testing is generally recommended.

How RPR test is made

The RPR test is a blood test, so it requires a blood sample. It’s actually a fairly labor intensive test for a laboratory to perform. In order to determine whether the test is positive or negative, a trained lab technician must look at each test individually. This process hasn’t been automated.

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RPR is known as a nontreponemal test. This is because it doesn’t look directly for the Treponema pallidum bacteria that cause syphilis, but instead looks for antibodies to the bacteria. Another type of nontreponemal test is known as VDRL, which is a very similar test. 

The rapid plasma reagin (RPR) test is commonly used as a screening test for syphilis. You can go to a laboratory to get blood drawn for this test. Another option is to order a home test kit. If you choose this option, you’ll take your blood sample yourself at home, using a fingerprick. This is a more convenient option for many people; however, it’s important to know that if you do get positive RPR results, then you’ll need to talk with a medical professional to discuss additional testing and treatment options.

How to interpret RPR test results

When you’re looking at your RPR results, they’re often reported as “reactive” or “nonreactive.” A reactive test is a positive test, while a nonreactive test is a negative test.

A positive RPR test means that you might have syphilis. It means that certain antibodies were found in your blood, which would be made if you had been exposed to syphilis. However, there are also other conditions that can cause a positive RPR test, including:

  • Other infections, such as tuberculosis, pneumonia, rickettsial disease, endocarditis, and malaria
  • Autoimmune disorders, such as lupus
  • Certain immunizations, including smallpox and Covid vaccination
  • Pregnancy

In general, it’s recommended that if you have a positive RPR test, you get a second test to confirm the presence of the syphilis bacteria. With a positive RPR, syphilis is a strong possibility, but this test alone can’t definitively diagnose syphilis.

It’s also important to know that the RPR test is sometimes negative in people who are in the early stage of syphilis, or people who are in the late stages of the disease. If you get a negative RPR test, but you’re at high risk for syphilis or have symptoms that may indicate syphilis, then another type of syphilis test may be recommended.

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FAQs

What is RPR in a blood test?

RPR stands for Rapid Plasma Reagin. This is a test that looks for antibodies against the bacteria that cause syphilis. If the antibodies are found, the test will be “positive” or “reactive.” This could mean that you have syphilis, although further testing is needed to be sure.

Do you need to do any preparation for the RPR test?

There’s nothing in particular that you need to do to get ready for the RPR test. You will need to give a blood sample, which may involve going to a laboratory or taking blood through a fingerprick at home.

What does a positive RPR blood test mean?

If your RPR test is positive, this means that you have antibodies in your blood that might indicate that you have syphilis. However, there are also other conditions that can cause these antibodies to be present, so you’ll need a follow-up test to be sure. With a positive RPR, diagnosis of syphilis is possible, but it’s not certain until you get another test for syphilis.

Sources

Clement ME, Hicks CB. RPR and the Serologic Diagnosis of Syphilis. JAMA. 2014 Nov 12; 312(18): 1922–1923. doi: 10.1001/jama.2014.2087

Henao-Martinez AF, Johnson SC. Diagnostic tests for syphilis. Neurol Clin Pract. 2014 Apr; 4(2): 114–122. doi: 10.1212/01.CPJ.0000435752.17621.48

Rapid Plasma Reagin. National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK557732/. Accessed 6 Oct 2022.

Sexually Transmitted Diseases (STDs): Data & Statistics. Centers for Disease Control and Prevention. https://www.cdc.gov/std/statistics/default.htm. Accessed 6 Oct 2022.

Syphilis: Sexually Transmitted Infections Treatment Guidelines, 2021. Centers for Disease Control and Prevention. https://www.cdc.gov/std/treatment-guidelines/syphilis.htm. Accessed 6 Oct 2022.


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