Syphilis is a sexually transmitted (venereal) disease caused by the spirochaete named Treponema pallidum. The Venereal Disease Research Laboratory test abbreviated vdrl test is a syphilis serology blood test and was developed by Harris, Rosenberg, and Riedel in 1946.During this test reagins, the non-treponemal antibody or antibodies react with a phospholipid, called cardiolipin to form aggregation
Principle of VDRL TEST
It is based upon the flocculation of antibody against the reaginic antigens in syphilitic infection caused by Treponema pallidum.
The test is more suitable as a syphilis screening agent than a syphilis diagnosis test. The presence of non treponema pallidum antibody in the patient’s serum is detected by using a non-specific antigen prepared from cardiolipin, lecithin and cholesterol.
Patients suffering from syphilis produce antibodies that react with cardiolipin antigen in a slide flocculation test, which is observed macroscopically as well as using a light microscope.
Reagent required for Vdrl serum Test
|VDRL Reagent||0.6 m||2-8 °C|
|Positive Control||0.2 ml||2-8 °C|
|Negative Control||0.2 ml||2-8 °C|
|Glass slide for VDRL||———–||———–|
|Disposable mixing sticks||———–||———–|
- Patient Test Serum Sample
How to carryout Vdrl syphilis test
- Before starting the test,Make sure you bring all reagents to room temperature and mix well and carefully read manufacturer’s instructions
- Take 20 µl of test sample in cavity of glass slide provided in the kit.
- Add 20 µl of VDRL reagent to the surface of the test sample in the same cavity.
Take note not to touch the tip to the liquid surface.
- Take 20 µl each of positive and negative control in different cavity.
- Then add 20 µl of VDRL reagent to both positive and negative control cavity.
- Mix well with disposable mixing sticks
- While mixing use different mixing stick every time
- Rotate the slide continuously for 4 minutes and observe for flocculation, which can be seen with naked eye or better under light microscope.
How to read Vdrl syphilis test results
After mixing the VDRL reagent with Positive control, Negative control and Test sample separately for 4 minutes observe for flocculation.
Flocculation in Test sample circle is considered a positive reaction which indicates the presence of treponemes at a significant and detectable level.
Causes of false positive result
- The reagents were mixed with each other
- Incubated for a longer time
Causes of false Negative result
- The reagents was not stored under proper conditions