The VDRL test is a screening test for syphilis. It measures substances, called antibodies, that can be produced in response to Treponema pallidum, the bacteria that causes syphilis.
The test is similar to the newer rapid plasma reagin (RPR) test.
Venereal disease research laboratory test
How the test is performed
The test is usually performed on blood. The VDRL test can be performed on spinal fluid if syphilis (neurosyphilis) may be present in individual's brain.
This article discusses the blood test.
Blood is 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.
How the test will feel
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
This test is used to diagnose syphilis. Syphilis is a highly treatable infection. In addition to screening individuals with signs and symptoms of sexually transmitted diseases, syphilis screening is a routine part of prenatal care during pregnancy. Several states also require screening for syphilis prior to obtaining a marriage license.
A negative test is normal and means that no antibodies to syphilis have been detected. The screening test is most likely be positive in secondary and latent syphilis. During primary and tertiary syphilis this test may be falsely negative.
What abnormal results mean
A positive test result may mean you have syphilis. If the test is positive, the next step is to confirm the results with an FTA-ABS test, which is a more specific syphilis test.
The VDRL test's ability to detect syphilis depends on the stage of the disease. The test's sensitivity to detect syphilis nears 100% during the middle stages; it is less sensitive during the earlier and later stages.
Some conditions may cause a false positive test, including:
- Lyme disease
- Certain types of pneumonia
- Systemic lupus erythematosus
What the risks are
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample 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)
The body does not always produce antibodies specifically in response to the syphilis bacteria, so this test is not always accurate.
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A.D.A.M. Editorial Team: David Zieve, MD, MHA, Greg Juhn, MTPW, David R. Eltz. Previously 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 (7/29/2009).
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