Medical Laboratory Technology-Juba South Sudan

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VDRL (Venereal Disease Research Laboratory) Test

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1. Objective

The objective of the test was to detect non-treponemal antibodies (reagin) in the blood, which appeared in response to cell damage caused by Treponema pallidum, the bacterium that causes syphilis.

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2. Principle

The VDRL test was a flocculation test. When the patient’s serum contained reagin antibodies, they reacted with cardiolipin-lecithin-cholesterol antigen and formed visible clumps (floccules) on a glass slide.

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3. Materials

Patient’s serum or plasma (no hemolysis)

VDRL antigen (prepared suspension)

Rotating mechanical shaker

Glass slide or ceramic plate with test circles

Pipette

Microscope (for confirmation if required)

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4. Procedure

1. 50 µL of patient serum was placed in a test circle on the slide.

2. 50 µL of VDRL antigen was added to the serum.

3. The slide was rotated on a mechanical shaker at 180 rpm for 4 minutes.

4. The mixture was observed for visible clumping.

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5. Result

Reactive (Positive): Fine clumps or floccules visible → Suggests syphilis infection

Non-Reactive (Negative): Smooth suspension without clumping → No antibodies detected

Weakly Reactive: Slight clumping, requires confirmation with treponemal tests

Note: A positive result should be followed by a confirmatory treponemal test (e.g., FTA-ABS, TPHA).

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6. Uses

Screening test for syphilis

Monitoring response to syphilis treatment

Not specific for T. pallidum – false positives may occur in pregnancy, malaria, autoimmune diseases

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7. Conclusion

The VDRL test served as an important screening tool for syphilis, but due to its non-specific nature, positive results required confirmation with specific treponemal tests.