Rapid plasma reagin test; Syphilis screening test
RPR (rapid plasma reagin) is a screening test for syphilis. It measures substances (proteins) called antibodies that are present in the blood of people who may have the disease.
No special preparation is usually needed.
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.
The RPR test can be used to screen for syphilis. It is used to screen people who have symptoms of sexually transmitted infections and is routinely used to screen pregnant women for the disease.
The test is also used to see how treatment for syphilis is working. After treatment with antibiotics, the levels of syphilis antibodies should fall. These levels can be monitored with another RPR test. Unchanged or rising levels can mean a persistent infection.
The test is similar to the venereal disease research laboratory (VDRL) test.
A negative test result is considered normal. However, the body does not always produce antibodies specifically in response to the syphilis bacteria, so the test is not always accurate. False-negatives may occur in people with early- and late-stage syphilis. More testing may be needed before ruling out syphilis.
A positive test result may mean that you have syphilis. If the screening test is positive, the next step is to confirm the diagnosis with a more specific test for syphilis, such as FTA-ABS. The FTA-ABS test will help distinguish between syphilis and other infections or conditions.
How well the RPR test can detect syphilis depends on the stage of the infection. The test is most sensitive (almost 100%) during the middle stages of syphilis. It is less sensitive during the earlier and later stages of the infection.
Some conditions may cause a false-positive test, including:
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
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. Philadelphia, PA: Elsevier; 2020:chap 237.
US Preventive Services Task Force (USPSTF); Bibbins-Domingo K, Grossman DC, et al. Screening for syphilis infection in nonpregnant adults and adolescents: US Preventive Services Task Force recommendation statement. JAMA. 2016;315(21):2321-2327. PMID: 27272583 pubmed.ncbi.nlm.nih.gov/27272583/.BACK TO TOP
Review Date: 9/1/2021
Reviewed By: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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