RPR (rapid plasma reagin) is a screening test for syphilis. It looks for antibodies that are present in the blood of people who have the disease.
The test is similar to the venereal disease research laboratory (VDRL) test.
Rapid plasma reagin test; Syphilis screening test
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
No special preparation is usually needed.
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, you may feel some throbbing.
The RPR test can be used to diagnose syphilis. It is used to screen people who have symptoms of sexually transmitted diseases and is routinely used to screen pregnant women for the disease.
Several states also require that couples be screened for syphilis before getting a marriage license.
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.
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 persons 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.
How well the RPR test can detect syphilis depends on the stage of the disease. 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 disease.
Some conditions may cause a false positive test, including:
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient 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:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Meyers D, Wolff T, Gregory K, et al; U.S. Preventive Services Task Force. U.S. Preventive Services Task Force recommendations for STI screening. Am Fam Physician. 2008 Mar 15;77(6):819-24.
Centers for Disease Control and Prevention, Workowski KA, Berman SM. Diseases characterized by genital ulcers. Sexually transmitted diseases treatment guidelines 2006. MMWR Morb Mortal Wkly Rep. 2006 Aug 4;55(RR-11):14-30.
Eckert LO, Lentz GM. Infections of the lower genital tract: vulva, vagina, cervix, toxic shock syndrome, HIV infections. In: Katz VL, Lentz GM, Lobo RA, Gershenson DM, eds. Comprehensive Gynecology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2007:chap 22.
Review Date: 7/26/2009
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Redmond, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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