Venereal disease research laboratory test; Syphilis - VDRL
How the Test is Performed
The test is most often 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.
How the Test will Feel
When the needle is inserted to draw blood, some people may feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
This test is used to screen for syphilis. The bacteria that cause syphilis is called Treponema pallidum.
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.
This test is similar to the newer rapid plasma reagin (RPR) test.
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 provider about the meaning of your specific test results.
What Abnormal Results Mean
A positive test result means you may 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
The body does not always produce antibodies specifically in response to the syphilis bacteria, so this test is not always accurate.
Veins and arteries vary in size from one person 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 lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Chernecky CC, Berger BJ. Venereal disease research laboratory test (VDRL) – serum. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:1165-1166.
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, Updated Edition. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 239.
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 www.ncbi.nlm.nih.gov/pubmed/27272583.