The Venereal Disease Research Laboratory (VDRL) test is a nonspecific flocculation test which is used for the screening of Syphilis. VDRL test is easy to perform and inexpensive, so it is commonly used in the screening of population for syphilis. Without some other evidence for the diagnosis of syphilis, a reactive nontreponemal test does not confirm Treponema pallidum infection.
Instead of checking for the bacteria that causes Syphilis, the VDRL test checks for the antibodies the body makes in response to antigens produced by cells that are damaged by the bacteria. Antibodies are a type of protein produced by the immune system to fight off invaders like bacteria or toxins. Testing for these antibodies can let the doctors know whether you have syphilis. One does not need to have the symptoms of syphilis for this test to be accurate because it checks for antibodies produced as a result of a syphilis infection, the VDRL test can be used regardless of whether you currently have any symptoms.
WHY DOCTORS PERFORM A VDRL TEST
Our doctors will most likely order a VDRL test if there’s a chance that a patient has syphilis. Early symptoms that may prompt the doctor to request for this test include:
- one small, painless sore
- swelling in lymph nodes near the sore
- a skin rash that doesn’t itch
In other cases, our doctors may screen for syphilis even if one does not have any symptoms or reasons to think they have Syphilis. A doctor will for example screen for syphilis as a routine part of pregnancy care. This happens to be a standard procedure, and it does not mean the doctor suspects syphilis.
Our doctors may also test for syphilis if the patient is being treated for another STI, e.g. Gonorrhea, or if one is infected with HIV, or if has engaged in high-risk sexual activity. If the patient has already been treated for syphilis, the doctor may recommend follow-up testing to be sure that the treatment worked and the infection has been cured.
In some cases, this test is needed for obtaining a marriage license or marriage certificate. Apart from its use to diagnose new infection, the physician may ask to perform the test to monitor the effectiveness of the treatment in patients who are found to be positive for syphilis.
VDRL test also helps in screening congenital syphilis in newly born babies, the test may sometimes give the false positive result. This is due to the transfer of antibodies from the infected mother to the child. In such case, the test are normally repeated after a month to confirm the result.
PREPARING FOR A VDRL TEST
Most people don't feel comfortable sharing the details of their sexual experiences, but the doctor's office is one place where you have to provide this information so that you can get the right care. The VDRL test doesn't require Patient to fast or stop taking any medications. If the doctor wishes to make an exception, he will inform the patient before the test. Should the doctor suspect that the syphilis infection has spread to the brain, a test of the spinal fluid may be ordered in addition to the blood test.
The most prudent preparation will be to follow the doctor's instructions on how to prepare for this test.
THE VDRL TEST
Usually, all that will be needed for the VDRL test is allow the healthcare professional to draw blood. Blood is generally drawn from a vein at the crease of the elbow or the back of the hand. This blood sample will then be sent to the laboratory and tested for the antibodies that may have been produced as a result of a syphilis infection.
There are three basic methods used in screening for syphilis. These include;
- Direct observation of the spirochete by dark field microscopy, and nontreponemal and Treponemal serologic antibody studies.
- Rapid Plasma Reagin (RPR) and the VDRL are used for initial screening, these are more sensitive nontreponemal tests such as the
- Specific Treponemal tests such as the fluorescent Treponemal antibody absorption (FTA-ABS) are used to confirm the diagnosis.
These screening tools have demonstrated a high accuracy for the clinical diagnosis of primary syphilis. This is a nonspecific test but which is useful in following treatment, because the antibody titer declines upon a successful therapy. Nontreponemal tests are rapid, simple, and inexpensive. They are the only tests recommended to monitor the course of disease during and after treatment. Nontreponemal tests can also serve to detect reinfection.
The main limitations of nontreponemal tests are their reduced sensitivity in primary syphilis and late latent syphilis, false-positive results due to cross reactivity, and the potential for false-negative results due to prozone phenomenon. Unfortunately, no current laboratory test can distinguish one trepanomatosis from another, and this must be considered in serology in areas of the world where yaws, pinta on endemic trepanomatosis exist.
The basis of the VDRL test is that the body produces antibodies when infected, and in this test the antibody is detected by subjecting the serum to an antigen, which is composed of colorless alcoholic solution of beef cardiolipin, cholesterol, and lecithin. It is a qualitative test for screening of syphilis, and currently all nontreponemal tests are flocculation tests and both VDRL and RPR tests are modifications of original Wasserman reaction. Unfortunately in this test, the antibody detects antigens, which are nonspecific, thereby yielding much false-positive reaction.
In a VDRL test, heated serum or unheated cerebrospinal fluid is mixed with Reagin (a purified mixture of lipids such as cardiolipin, lecithin, and cholesterol) on a glass slide. Flocculation, or clumping, of the mixture is then read microscopically as either “reactive” (if clumping occurs) or “nonreactive” (if there is no clumping).
UNDERSTANDING A VDRL TEST RESULTS
If the test returns negative for syphilis antibodies, the result suggests that the patient has no syphilis infection.
If the test returns positive for syphilis antibodies, it suggests that the patient probably (but not definitely) has syphilis. If this occurs, the doctor will order a more specific test to confirm the results. A Treponemal test is often used to confirm the positive test. A Treponemal test will check whether the immune system has produced specific antibodies in direct response to the syphilis-causing Treponema pallidum.
POTENTIAL FOR FALSE POSITIVES AND NEGATIVES
VDRL tests are not always accurate. For example, a test may return false-negative results if the patient had had the syphilis infection for less than three month. This is because it could take this long for the body to make antibodies. The test is also unreliable in late-stage syphilis.
The following conditions can cause false-positive results;
- Lyme disease
- Pneumonia (N.B. certain types only)
- Systemic lupus erythematosus
- IV drug use
It is also possible in some cases, that the body may not produce antibodies even if the patient has been infected with syphilis. This means the VDRL test will be inaccurate.
Conversely, the antibodies that are produced as a result of a syphilis infection can stay in the body even after the syphilis has been treated. This means might always lead to positive results for this test.
RISKS OF TAKING THE VDRL TEST
The risks of a blood draw are fairly minor or none existent. Slight issues like mild pain during the blood draw or minor bruising or bleeding afterward might be experienced. The development of a serious problem from a blood draw, such as inflammation of the vein or an infection, is rare.
Syphilis is treatable however, it’s important to consult a doctor as soon as one thinks she/he might have been exposed. The infection can spread through the body and cause complications in the organs if left untreated. The VDRL test may not be perfect, but it remains a trusted test that can be a first step in helping to determine the presence of an infection.
Bottom line is to remember is to practice safe sex, and immediately one thinks he/she has had contact with syphilis, he/she must see a doctor immediately.