What is VDRL Test: Purpose, How to Read & Measure Accuracy

Syphilis, a sexually transmitted infection (STI), is a common health concern in recent times. The bacterium Treponema pallidum is usually responsible for causing this. Therefore, health researchers have developed the VDRL test to determine if you have this condition.

Are you worried about having syphilis and trying to get it verified with a VDRL test? This article will give you a complete guide about its procedure and risks.

The full form of the VDRL test is the Venereal Disease Research Laboratory test. A standard blood test used in healthcare settings, the VDRL test, helps to identify the presence of syphilis in your body. This test does not look for bacteria that causes this condition but instead looks for the antibodies that your body makes while responding to the antigens produced to damage the bacteria. Your immune system produces these antibodies to fight against bacteria and toxins.

When doctors conduct this test, it helps them confirm if you have this disease. For example, if you have the following symptoms of syphilis, doctors are more likely to suggest this test.

• Small areas of a painless sore
• Swollen lymph nodes near the sore
• Non-itchy skin rashes

Thus, if you wonder what a VDRL test means, it is a nontreponemal test mainly used to confirm the infection with a treponemal test specific to syphilis. Doctors conduct the examination either through blood or the cerebral spinal fluid (CSF). Now, if you wonder about the procedure of a VDRL test, it is done in two ways, as described below.

• Blood test: A healthcare professional will draw blood from your vein and send it for testing in a lab. If the results show that syphilis has spread to your brain, the doctor will also test your spinal fluid.
• CSF collection: Healthcare professionals use a lumbar puncture or spinal tap for collecting CSF. Once you lie down, the professional will insert a spinal needle into your lower spine and extract a small quantity of CSF. They will then send it for testing.

No preparation is needed for a VDRL test. Also, there are no drinking or eating requirements before taking the test.

Now that you know what the VDRL test is, you must be curious to know how to read it. Once the doctors take your sample for testing, the report takes about 3-5 days to come. The process is simple, as reading includes only positive or negative. If your VDRL test report shows negative, it suggests that you do not have syphilis. Likewise, a negative VDRL blood test indicates no evidence of infection. However, a negative CSF report does not rule out a diagnosis of neurosyphilis.

On the other hand, a positive VDRL test means syphilis antibodies are present in your body. However, such a result is not always accurate. Other infections such as HIV or pneumonia and other autoimmune diseases can trigger a false-positive report. If your blood test comes positive, your doctor might ask you to do a fluorescent treponemal absorption assay test to confirm if the existing infection is syphilis. On the other hand, they might ask you to do a syphilis-specific treponemal test if you get a positive CSF report.

While a VDRL test is accurate, sometimes it might generate false-positive and false-negative results. A past survey in 2016 shows among 1926 patients, about 52 of them had genuinely positive results, and 11 of them had false-positive reports. In some cases, a VDRL test report might be positive even in the absence of syphilis. Other infections and health conditions might trigger a positive result. For example, if you suffer from the following conditions, you might receive a positive report.

• Lupus
• Infectious mononucleosis
• Antiphospholipid antibody syndrome
• Leprosy
• Hepatitis A
• Malaria
• Tuberculosis
• IV drug use
• Lyme disease

Occasionally, if you take a VDRL test during pregnancy, you can end up receiving a positive report even in the absence of syphilis. Therefore, it is advisable to conduct additional diagnoses even after receiving a positive VDRL test report.

In some cases, your body may fail to produce antibodies even if you have a syphilis infection. As a result, the VDRL test will not detect it. Moreover, the antibodies can continue to stay even after you have completed your syphilis treatment. In such conditions, this test can produce false-negative reports.

Now that you know why a VDRL test is done, you must be worried about its possible risks. It is safe to say that there are no significant risks associated with this test. However, you might face the following mild complications after a blood VDRL test.

• Pain near the injection site
• Bruising or bleeding in the injection site
• Dizziness and light-headedness

If you undergo a lumbar puncture, on the other hand, the following risks might apply to you.

• A mild or severe headache
• Lower back pain
• Pain in the leg
• Bleeding or infections in the injection site 
• Numbness or tingling in the lower back or legs

Syphilis sounds like a life-threatening disease, but it can be curable. However, proper treatment is essential from the very beginning. You should immediately take a VDRL test as soon as you feel the symptoms. If you leave it untreated, syphilis can cause significant harm to multiple organs. While this test might not be completely accurate, it is an effective way to determine if you might have the infection and thereby begin a preliminary treatment.

Therefore, as you can see, a VDRL test can help identify the chances of syphilis infection. It is mainly conducted once you start getting the symptoms, and doctors do it either by testing blood or CSF. Even though it might generate false-positive or false-negative results, this test is preferred for detecting such conditions in the healthcare sector.