The laboratory procedure for venereal disease research (VDRL) is a blood test that can recognize infections with the syphilis. Syphilis is one of Sexually Transmitted Infections (STIs) most common.
In 2018, 115,045 new cases of syphilis were identified in the Centers for Disease Control and Prevention (CDC).
Untreated syphilis, including the brain, spinal cord and heart, can damage vital organs.
Doctors can diagnose syphilis and other early stage STIs with the help of screening and testing procedures.
This article looks at the VDRL test which is one form of screening test for syphilis.
What is it?
The VDRL test is one of three nontreponemal tests for syphilis detection. Nontreponemal tests are not objective for syphilis and may show false-positive results.
Doctors can not single-handedly diagnose syphilis infections based on positive VDRL tests alone. We need a treponemal test, which is specific to syphilis, to confirm the infection.
A doctor may do a VDRL test on either the blood or the spinal cerebral fluid (CSF).
Usually, a CSF VDRL test happens when a doctor believes the syphilis is at a more advanced stage when it can affect the brain and central nervous system. That is known as neurosyphilis.
A doctor can extract CSF for this examination through a procedure called a lumbar puncture which is also known as a spinal tap.
How does it work?
The bacterium Treponema pallidum (T. pallidum) causes infections with the syphilis.
If T. Pallidum enters the body, and the immune system produces antibodies that are proteins that destroy bacteria that invade it.
The VDRL test fails to respond to the T. Bacterium pallidum. Rather, the test tests the amount of antibodies in the blood, or CSF.
Healthcare providers collect a sample of blood or spinal fluid and send it out to a laboratory where it is tested for antibodies by a technician.
A blood test with VDLR involves adding to the blood sample a colorless alcoholic solution consisting of cardiolipin, lecithin, and cholesterol.
A CSF test involves the addition of a lipid mixture, called reagin. It suggests a positive reaction if clumping happens, and hence the presence of syphilis.
Health care providers conduct VDRL tests in most cases by taking blood samples. They can perform the test though using a CSF sample.
A blood test requires the injection of a hollow needle into a vein in the elbow or back of the hand by a health care provider.
The blood flows into an airtight collection tube that is attached to the other end.
Before inserting the needle, a healthcare provider may tie a rubber band or tourniquet above the injection site to make it easier to locate the veins.
CSF samples are obtained by health care providers through a process known as a lumbar puncture or spinal tap.
A person will lie on their side during the procedure and pull their knees towards their chest.
The healthcare provider will disinfect the injection site with a local anesthetic and become numb.
They will then insert a spinal needle into the lower spine which is used to extract a small amount of CSF.
What do the results mean?
The laboratory will forward the findings to the physician who ordered the examination.
The physician will clarify the test results of a person either at a follow-up appointment or over the phone.
The trial can take 3–5 days.
Negative test results typically mean that the blood does not contain any antibodies to syphilis.
A negative result of a VDRL blood test suggests that there is no evidence of an infection.
People who get a negative result usually don’t need additional testing.
People with a high risk of syphilis, however, may want to consider getting routine screening tests about every three months.
According to the New York City Department of Health and Mental Hygiene Bureau of Sexually Transmitted Infections, a negative CSF result does not rule out a diagnosis of neurosyphilis.
A positive result means that the VDRL test detected the presence of the syphilis antibodies.
The blood test with VDRL isn’t always successful. Infections like HIV or pneumonia and other autoimmune disorders can cause a false-positive outcome.
If the result is positive, another test, such as the fluorescent treponemal absorption assay, will be carried out by a doctor. The test will decide if the infection is syphilis.
A doctor will typically recommend a CSF VDRL test when they believe a individual may have late syphilis stages.
Usually, if a person is given a positive result, a doctor may conduct a treponemal test that detects the antibodies to the T Pallidum proteins. If this is positive it means that the central nervous system has been compromised with syphilis.
However, sometimes the doctors test in reverse for syphilis. They will start by testing a person with a tréponemal test specific to syphilis. If this proves positive, they will carry out a nontreponemal test, like a VDRL
The VDRL test provides a safe and convenient screening method for syphilis infections. The evaluation itself bears no significant risks.
However, the method of drawing blood and lumbar punctures can pose some minor complications.
Blood draws could cause:
- tenderness or pain near the injection site
- bruising or bleeding immediately after the procedure
Although rare, a lumbar puncture can cause the following complications:
- a mild to severe headache
- numbness or tingling in the lower back or legs
- lower back or leg pain
- infections at the injection site
When to see a doctor
The United States Preventative Services Task Force (USPSTS) recommend screening for syphilis infections in the following populations:
- men who have sex with men
- people living with HIV
- pregnant women
A doctor may use a VDRL test to screen for syphilis if someone:
- has symptoms of syphilis
- has recently been treated for syphilis
- believes they may have had exposure to T. pallidum
- is currently receiving treatment for another STI
- engages in sexual activity without the use of barrier contraceptives
A person should get tested for syphilis if they experience the following symptoms.
- The appearance of a chancre: This is a painless, round, firm sore. The chancre will heal after 3–6 weeks, even if a person does not receive treatment.
- The appearance of rashes or sores: The rash may be red and rough, and sores may appear on areas of the body.
Other symptoms may include swollen lymph glands, fever, hair loss, weight loss, and headaches.
Symptoms of syphilis vary according to the stage of the disease.
A chancre appears during the primary stage of syphilis. It will appear where the infection entered a person’s body.
If a person does not receive treatment, syphilis will develop into the secondary stage.
This is when skin rashes and lesions appear. They may occur in the vagina, the anus, or the mouth.
The rashes are not typically itchy.
A person may also develop a fever, muscle aches, swollen lymph glands, sore throat, and hair loss.
No symptoms of syphilis appear in this stage.
This stage can be fatal and typically occurs between 10–30 years after the initial infection.
It can affect the brain, eyes, heart, blood vessels, joints, and bones.
The symptoms may vary depending on which organ the syphilis is affecting.
Neurosyphilis and Ocular Syphilis
This may happen at any stage of the infection. Ocular syphilis affects the body, and neurosyphilis affects the nervous system and the brain.
Signs include anxiety, fatigue, depression, physical function issues and behavioral changes.
Doctors and other healthcare providers can screen for syphilis using the VDRL test. Syphilis is an STI resulting from T. Bacterium pallidum.
Antibodies that kill bacteria and other potentially harmful microbes are produced by the body’s immune system.
The VDRL test measures how many antibodies are present in the blood or spinal fluid of a person.
A health care provider will need to collect blood or a sample of spinal fluid to perform the test.
These procedures can cause minor side effects near the injection site, such as headaches, bruising and soreness.
Those who most likely have negative outcomes don’t have syphilis. Nevertheless, if someone has a recent exposure or has a high risk for syphilis, a doctor might suggest repeating the test at a later date.
Early detection of syphilis will lead to better, more effective treatment outcomes.
Early treatment reduces the risk of complications in the long term, which helps prevent further transmission.