The VDRL test is a screening test for syphilis. It measures substances, called antibodies, that your body may produce if you have come in contact with the bacteria that causes syphilis. This bacteria is called Treponema pallidum.
The test is similar to the newer
Venereal disease research laboratory test
How the test is performed
The test is usually done using a blood sample. It can also be done using a sample of spinal fluid. This article discusses the blood test.
A blood sample is needed. For information on how this is done, see:
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 screen for syphilis. Your health care provider may order this test if you have signs and symptoms of a sexually transmitted illness (STI).
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. It means that no antibodies to syphilis have been seen in your blood sample.
The screening test is most likely to be positive in the secondary and latent stages of syphilis. This test may give a false-negative result during early- and late-stage syphilis. This test must be confirmed with another blood test to make the diagnosis of syphilis.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
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.