A 24-year-old woman donating blood is found to have a reactive VDRL at a dilution of 1:2. She is asymptomatic, has no sexual risk factors, and the FTA-ABS test is non-reactive. She gives a history of an episode of fever with chills treated as vivax malaria last year. This serological pattern is best explained by:

• A Early primary syphilis before treponemal antibody development
• B Biological false positive reaction due to prior malaria ✓
• C Prozone phenomenon causing a falsely low VDRL titre
• D Seronegative latent syphilis

Explanation

Nontreponemal tests detect reagin antibodies against cardiolipin-lecithin-cholesterol antigen and are prone to biological false positivity in conditions associated with altered phospholipid immunity, including malaria, leprosy, infectious mononucleosis, autoimmune disease such as SLE, pregnancy and injection drug use. A reactive VDRL with a repeatedly non-reactive treponemal test confirms a false positive result. Prozone refers to falsely negative undiluted sera in high-titre infection, and seronegative syphilis would show a reactive treponemal test.

Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.