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VDRL

Definition

VDRL is a screening test for syphilis that measures antibodies that can be produced by Treponema pallidum, the bacteria that causes syphilis.

The test is similar to the newer rapid plasma reagin (RPR) test.

Alternative Names

How the test is performed

The test is usually performed on blood. If an individual is suspected of having brain involvement with syphilis (neurosyphilis), the VDRL test may be performed on spinal fluid.

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.

Normal Values

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.

The following conditions may cause a false positive test:

• HIV
• Lyme disease
• Certain types of pneumonia
• Malaria
• 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)

Special considerations

The body does not always produce antibodies specifically in response to the syphilis bacteria, so this test is not always accurate.

References

Review Date: 6/18/2007

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