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Syphilis:- Part 2 – VDRL (Venereal disease research laboratory test)

March 24, 2023Lab TestsMicrobiology

VDRL (Venereal disease research laboratory test)

Sample for VDRL test

  • This is done on the serum of the patient.

Purpose of the test (Indication)

  • This is a screening test for syphilis.

Syphilis microbiology

  1. Syphilis is a venereal disease.
  2. The causative agent for syphilis is Treponema pallidum, which is a spirochete.
  3. The spirochete is 8 to 15 µm in length, gram-negative organisms.
Treponema pallidum structure

Treponema pallidum structure

  1. Spirochaetes are microaerophilic, but this organism cannot be cultured in vitro.
  2. This is motile with rotation around its long axis and flexion and extension laterally.
  3. T.pallidum survives in the patient with syphilis, and it has no other habitat.
  4. The untreated disease has three stages, which may last many years.
    1. Primary stage.
    2. Secondary stage.
    3. Tertiary stage.
Clinical course of syphilis

The clinical course of syphilis

VDRL (Venereal disease research laboratory)

  1. This test will detect antibodies against Treponema Pallidum, which appears in 4 to 6 weeks.
  2. VDRL is a nontreponemal test that detects reagin and antibodies that act against cardiolipin as an antigen.
  3. During primary and tertiary syphilis, the test may be falsely negative.
  4. Another nontreponemal test is Rapid plasma reagin (RPR).
  5. VDRL is a screening test.
    1. VDRL may show the negative result is late syphilis.
  6. Other treponemal antibody tests are:
    1. TP-PA ( particle agglutination T.pallidum ).
    2. FTA-ABS ( fluorescent treponemal antibody test).

VDRL test principle

  1. This test is performed using a cardiolipin-lecithin cholesterol antigen.
  2. Heat-inactivated serum from the patient is used.
  3. Cardiolipin is prepared from beef heart.
Principle of VDRL test

Principle of VDRL test

  1. This test can also be done on the CSF as well.
  2. Advantage:
    1. This is inexpensive.
    2. This is reproducible.
  3. Disadvantage:
    1. Not 100% specific for syphilis.
    2. Confirm by FTA-ABS or TP-MHA test.
    3. Run positive and negative control.

NORMAL VDRL

  • A negative test means that no antibody to syphilis has been detected.
  • This screening test is most likely positive for Secondary and latent syphilis.

Negative VDRL

  1. No syphilis.
  2. Done when antibodies are still not developed.
  3. In the late or inactive phase.
  4. The patient has an immune deficiency.
  5. Lab error.

False-positive test

  1. HIV
  2. Lyme disease
  3. certain types of pneumonia
  4. Malaria
  5. Systemic lupus erythematosus.

Questions and answers:

Question 1: Can you get a false positive VDRL test?
Show answer
Yes, you can get in HIV infection and a few more conditions.
Question 2: What is the principle of VDRL test?
Show answer
Antibodies in the patient react with cardiolipin.

Possible References Used
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