Syphilis – Part 2 – V.D.R.L (Venereal disease research laboratory test)
- This is done on the serum of the patient.
Purpose of the test (Indication)
- This is a screening test for syphilis.
- Syphilis is a venereal disease.
- The causative agent for syphilis is Treponema pallidum, which is a spirochete.
- The spirochete is 8 to 15 µm in length, gram-negative organisms.
- Spirochaetes are microaerophilic but this organism cannot be cultured in vitro.
- This is motile with rotation around its long axis as well as flexion and extension laterally.
- T.pallidum survives in the patient with syphilis and it has no other habitat.
- The untreated disease has three stages and these may last for many years.
- Primary stage.
- Secondary stage.
- Tertiary stage.
- This test will detect antibodies against Treponema Pallidum, and these antibodies appear in 4 to 6 weeks.
- VDRL is a nontreponemal test that detects reagin and antibodies that act against cardiolipin as an antigen.
- During primary and tertiary syphilis the test may be falsely negative.
- Another nontreponemal test is Rapid plasma reagin (RPR).
- VDRL is a screening test.
- VDRL may show the negative result is late syphilis.
- Other treponemal antibody tests are:
- TP-PA ( particle agglutination T.pallidum ).
- FTA-ABS ( fluorescent treponemal antibody test.
VDRL test principle
- This test is performed using a cardiolipin-lecithin cholesterol antigen.
- Heat-inactivated serum from the patient is used.
- This test can also be done on the CSF as well.
- This is inexpensive.
- This is reproducible.
- Not 100% specific for syphilis.
- Confirm by FTA-ABS or TP-MHA test.
- Run positive and negative control
- A negative test means that no antibody to syphilis has been detected.
- This screening test is most likely positive for Secondary and latent syphilis.
- No syphilis.
- Done when antibodies are still not developed.
- In the late or inactive phase.
- The patient has an immune deficiency.
- Lab error.
- Lyme disease
- certain types of pneumonia
- Systemic lupus erythematosus.