What is a VDRL Test?
The venereal disease research laboratory (VDRL) test is designed to assess whether or not you have syphilis, a sexually transmitted infection. Instead of testing for the bacteria that causes syphilis, the VDRL test checks for antibodies to this bacteria. Your immune system produces a specific kind of antibody (a type of protein) when it defends your body from syphilis. Testing for this antibody can let your doctors know whether you have syphilis.
You do not need to have signs or symptoms of syphilis for this test to be accurate. Because it checks for syphilis antibodies, it can be used regardless of whether you currently have any symptoms.
Why Doctors Perform a VDRL Test
A VDRL test checks for syphilis, so your doctor may order the test if there is a chance that you have this disease. In some cases, your doctor will order the test if you show signs of syphilis. Possible early symptoms, which may prompt your doctor to order this test, include:
- one small, painless sore
- swelling in lymph nodes near the sore
- skin rash that does not itch
In some cases, your doctor may screen for syphilis even if you do not have any symptoms or reasons to think you have the disease. For example, if you are a pregnant woman, your doctor will screen for syphilis as a routine part of your care. This is standard procedure and does not mean that your doctor actually thinks that you have syphilis.
The VDRL Test
Usually, all you need to do for the VDRL test is allow a doctor to draw your blood. This blood sample will then be taken away and tested in a laboratory for the antibody to syphilis. In some cases, your doctor may choose to test your spinal fluid instead of your blood.
The VDRL test generally doesn’t require you to fast or stop taking any medications in preparation. If your doctor wants to make an exception, he or she will let you know before your test.
Understanding the Results of Your VDRL Test
Ideally, your test should come back negative for syphilis antibodies. This suggests that you do not have syphilis.
If your test comes back positive for syphilis antibodies, you probably (but not definitely) have syphilis. If this occurs, your doctor will order a more specific test to confirm the results.
Potential for False Positives and Negatives
Unfortunately, the VDRL is not always accurate. For example, you may have false negative results if you have had syphilis for less than three months, as your body might take this long to make antibodies. The test is also unreliable in late-stage syphilis.
On the other hand, you may receive false positive results if you have:
- Lyme disease
- systemic lupus erythematosus
In some cases, your body may not produce antibodies to syphilis even if you have been infected. This means, of course, that this test will be inaccurate.
The antibodies to syphilis can stay in your body even after your syphilis has been treated. This means you might always have positive results on this test.
Risks of Taking the VDRL Test
The risks of a blood draw are fairly minor. You might have slight issues like mild pain during the blood draw or minor bruising or bleeding afterward. Developing serious problems from a blood draw, such as inflammation of the vein or an infection, is rare.