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Diagnostic Tests – VDRL and RPR (Nontreponemal Tests)

1. For which disease(s) are these tests used?

VDRL (Venereal Disease Research Laboratory) and RPR (Rapid Plasma Reagin) are nontreponemal serologic tests used for the screening and diagnosis of syphilis. They detect antibodies directed against cardiolipin released from damaged host cells and treponemes.

2. What signs and symptoms would you expect?

Clinical features vary by stage:

  • Primary syphilis
    • Painless chancre
    • Painless regional lymphadenopathy
  • Secondary syphilis
    • Diffuse rash (often involving palms and soles)
    • Generalized lymphadenopathy
    • Condylomata lata
    • Patchy alopecia
  • Tertiary syphilis
    • Cardiac disease (e.g., aortitis)
    • Neurologic disease (neurosyphilis)
    • Gummatous lesions
3. When can you get false-negative and false-positive results?

  • False positives may occur with:
    • Connective tissue diseases
    • Infectious mononucleosis
    • Malaria
    • Leprosy
    • IV drug use
    • Hepatitis C
    • Infective endocarditis
    • Pregnancy
  • False negatives:
    • Prozone phenomenon, caused by very high antibody titers that interfere with test reactivity
4. What test do you do if suspicion is high but VDRL/RPR is negative?

If clinical suspicion remains high:

  • Primary syphilis → Darkfield microscopy of the chancre
  • Other stages → FTA-ABS (Fluorescent Treponemal Antibody–Absorption test)

5. What is the response to treatment?

  • VDRL and RPR titers decrease or become negative with successful treatment → useful for monitoring response
  • FTA-ABS may remain positive for life, even after adequate therapy

High-yield exam pearls
  • Screening & monitoring → VDRL / RPR
  • Confirmation → FTA-ABS
  • Early primary lesion → Darkfield examination




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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.