A patient is tested for syphilis. VDRL test is positive at 1:8 dilution. To confirm the diagnosis, the specific treponemal test used is:

• A Rapid Plasma Reagin (RPR) test
• B Widal test
• C Treponema pallidum Hemagglutination Assay (TPHA) ✓
• D Weil-Felix reaction

Explanation

VDRL and RPR are non-treponemal (reagin) tests that detect antibodies to cardiolipin-lecithin-cholesterol antigen and are used for screening and monitoring treatment response; they can give biological false-positive results in conditions like SLE, malaria, viral infections, and pregnancy. Confirmation requires a specific treponemal test that detects antibodies against T. pallidum antigens: TPHA (Treponema pallidum Hemagglutination Assay) or FTA-ABS (Fluorescent Treponemal Antibody Absorption) test. Once reactive, treponemal tests remain positive for life even after successful treatment and cannot monitor cure.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.