Serology workflow: the VDRL (Venereal Disease Research Laboratory) test for syphilis is commonly performed as which procedural format?
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ATube test (macroscopic precipitation in tubes)
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BRing test (antigen–antibody ring at interface)
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CSlide test (flocculation on a glass slide)
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DNone of these
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EMicrotiter plate ELISA
Answer
Correct Answer: Slide test (flocculation on a glass slide)
Explanation
Introduction / Context:The VDRL test is a nontreponemal screening assay for syphilis that detects reagin antibodies against cardiolipin–lecithin–cholesterol antigen. Correctly identifying the test format helps in understanding its performance characteristics, interpretation, and limitations.
Given Data / Assumptions:
- VDRL is a nontreponemal test (screening).
- It uses a standardized antigen and observed flocculation.
- The question asks about the procedural format.
Concept / Approach:VDRL is traditionally performed as a slide flocculation test. Patient serum (often heat-inactivated) is mixed with antigen on a glass slide and observed microscopically for flocculation. RPR is a related macroscopic cardiolipin test but uses charcoal particles for easier visualization.
Step-by-Step Solution:
1) Recall that VDRL = slide test (microscopic reading).2) Distinguish from RPR (charcoal-enhanced macroscopic reading).3) Choose “Slide test” as the correct format.Verification / Alternative check:Standard lab manuals describe VDRL as a microscopic slide flocculation assay, with titers reported for reactive specimens.
Why Other Options Are Wrong:
- Tube/ring tests: Not the standard for VDRL.
- None of these / ELISA: Not correct; VDRL is not an ELISA.
Common Pitfalls:
- Confusing VDRL with RPR (both are nontreponemal but differ in visualization method).
Final Answer:Slide test (flocculation on a glass slide)