VDRL (Venereal disease research laboratory test)

What sample is needed for the VDRL test?

• This is done on the patient’s serum.

What are the indications for the VDRL test?

• This is a screening test for syphilis.

How will you discuss 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.

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

VDRL (Venereal Disease Research Laboratory) Test

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).

What is the principle for the VDRL test?

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.

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

What is the normal VDRL test report?

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

What are the causes of negative VDRL tests?

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.

What are the causes of false-positive tests?

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

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