A 30-year-old HIV-positive man presents with painless inguinal swelling. Aspiration reveals 'sulcus sign' — groove sign above and below Poupart's ligament. Which serological test confirms the causative agent?
- A VDRL — Treponema pallidum
- B Complement fixation test (Frei test equivalent) — Chlamydia trachomatis L1/L2/L3 ✓
- C ELISA for Klebsiella granulomatis — donovanosis
- D Culture for Haemophilus ducreyi — chancroid
Correct answer: B. Complement fixation test (Frei test equivalent) — Chlamydia trachomatis L1/L2/L3
Explanation
The groove sign (sign of Greenblatt) — inguinal lymphadenopathy divided by Poupart's (inguinal) ligament into upper and lower components — is pathognomonic of lymphogranuloma venereum (LGV) caused by Chlamydia trachomatis serovars L1, L2, L3. Serological confirmation uses complement fixation test (titre >1:64) or microimmunofluorescence. The Frei test (intradermal antigen test) is now obsolete. Treatment is doxycycline 100 mg BD for 21 days or erythromycin for 3 weeks.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.