The Venereal Disease Research Laboratory (VDRL) test screens for the antibodies produced by the body in response to the presence of Treponema pallidum, a bacterium that causes syphilis. VDRL is just one of the tests to make a presumptive diagnosis of Syphilis. It is a highly sensitive blood test. It is also performed as a part of routine examination during pregnancy.
Factors involved to understand the normal range of VDRL levels:
A negative test result is the normal result of the VDRL test. Normal range, type of measurement, and samples used for the test vary according to different laboratories.
Negative test results indicate there is no infection present. However, negative test result only indicates there is no evidence of infection at the time of the test. Infection may take from several weeks upto 3 months to present itself, so a repeat testing at a later date is often recommended. The test is unreliable in late-stage syphilis too.
Positive test results indicate that the patient may have syphilis. The positive result, however, does not guarantee the presence of syphilis. After a positive result is obtained, it is necessary to confirm the results with Fluorescent Treponemal Antibody Absorption (FTA-ABS) test. A positive FTA-ABS test is a sign of syphilis infection.
Early symptoms such as a small, painless sore, swollen lymph nodes, and skin rashes that don’t itch, may prompt the doctor to order this screening test.
The sensitivity of the VDRL test depends upon the stage of infection. The test is highly sensitive during the middle stages but is less sensitive during the primary and later stages. Some other conditions present at the same time may interfere with the test to give false positive results.
These conditions include:
Antibodies may not always be produced in response to syphilis bacteria and this may give false negative results.
Preventive measures can be taken to reduce the risk of syphilis. This includes abstaining from unprotected and risky sexual activities, refraining from alcohol and drug use, using condoms, have regular testing done for STIs, etc. This can help prevent the spread of these infections.
VDRL test is a simple blood test and has no major risks associated with it. Some of the risks associated with collecting a blood sample may include excessive bleeding at the site of puncture, fainting, hematoma, or infection at the site of puncture. These complications don’t require treatment.
Depending upon the severity of infection, samples can also include CSF, skin samples, and tissue samples. The collection of these samples may cause some discomfort, but there are no risks associated with it.
VDRL test often gives false negative results in early and late stage of the infection. Hence, it is important to confirm the diagnosis of the syphilis with other blood tests. Other tests such as Rapid Plasma Reagin (RPR) Test, Rapid immunochromatographic test, and Fluorescent Treponemal Antibody Absorption (FTA-ABS) test, are often recommended to screen for the presence of syphilis infection.
The VDRL usually becomes reactive within the first few weeks after infection, peaks during the first year, and then slowly declines, so that low titers (levels) are seen in late syphilis. Advanced tests such as Enzyme Immunoassay (EIA) test, FTA-ABS test, Treponema pallidum particle agglutination assay, etc. are ordered to confirm the diagnosis of syphilis infection. Other tests such as HIV test, gonorrhea test, and other STIs screening are also ordered.
Post Treatment, the patient is asked to repeat quantitative nontreponemal serological testing like VDRL/RPR and clinical evaluation at 3, 6, and 12 months for confirmation. If these tests are negative, patient is assured to be cured.
VDRL test screens for the presence of antibodies and hence is not dependent on the symptoms. The test does not require any special preparations. However, conditions such as use of antibiotics before the test, presence of another disease or infection, etc. can interfere with the test results. In such cases, it is important for the patient to consult with their health care provider to be more clear about the test.
Results are often obtained within 3-5 days. Further blood work or repeat testing may be recommended within 2 to 4 weeks. The test is also used to monitor the progress and effectiveness of the treatment. VDRL test is also a good way to screen for the risk for possible sexually transmitted infections (STIs).
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