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Diagnostic Test – Darkfield Microscopy
1. What is this?

Darkfield microscopy is the most accurate diagnostic test for primary syphilis.
It allows direct visualization of Treponema pallidum, the causative organism, from an active lesion.


2. How is it done?

  • A scraping or swab is obtained from a syphilitic chancre
  • The specimen is placed on a glass slide
  • The slide is examined using darkfield illumination
  • Motile spirochetes can be seen directly if T. pallidum is present
This technique relies on live organisms, making proper specimen handling essential.

3. When do you select darkfield microscopy?

Choose darkfield microscopy when:


  • The clinical scenario suggests primary syphilis
  • The question asks for the most accurate diagnostic test
  • There is a painless genital ulcer (chancre)​
Key test-taking point:


  • In primary syphilis, RPR and VDRL have a false-negative rate of ~25%
  • Darkfield microscopy is more sensitive than RPR or VDRL in this stage



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Kembara Xtra 

Facts about medicine and its subtopic such as anatomy, physiology, biochemistry, pharmacology, medicine, pediatrics, psychiatry, obstetrics and gynecology and surgery.