A 28-year-old woman presents to the gynaecology outpatient clinic with a 6-week history of mucopurulent cervical discharge and lower abdominal pain. She is sexually active with a single partner. On examination, she has cervical motion tenderness and adnexal tenderness bilaterally. Her urine pregnancy test is negative. Nucleic acid amplification test (NAAT) on a cervical swab is positive for Chlamydia trachomatis. She denies any systemic symptoms, fever, or joint pain. What is the most appropriate next step in management?

Explanation

## Diagnosis and Clinical Context **Key Point:** This patient has uncomplicated cervicitis with pelvic inflammatory disease (PID) caused by *Chlamydia trachomatis*, confirmed by NAAT — the gold standard nucleic acid test for chlamydial detection. ## First-Line Treatment for Uncomplicated Chlamydial Infection | Regimen | Dosing | Indication | Notes | |---------|--------|-----------|-------| | **Doxycycline** | 100 mg BD × 7 days | Uncomplicated urogenital infection (non-pregnant) | **First-line** — excellent tissue penetration, cost-effective | | Azithromycin | 1 g single dose | Alternative if doxycycline contraindicated | Emerging resistance; no longer preferred monotherapy | | Ceftriaxone | 250 mg IM single dose | Gonorrhoea (not chlamydia monotherapy) | Used in dual therapy for gonorrhoea + chlamydia co-infection | | Fluoroquinolones | Variable | Not recommended | Resistance patterns; inferior efficacy | **High-Yield:** Doxycycline 100 mg BD for 7 days is the **WHO and CDC preferred first-line agent** for uncomplicated *C. trachomatis* infection in non-pregnant women. It achieves high intracellular concentrations and excellent cure rates (>95%). ## Why Doxycycline Over Alternatives? 1. **Azithromycin (1 g single dose):** While acceptable, increasing resistance rates and macrolide-resistant strains have reduced its preference. Single-dose convenience does not outweigh efficacy concerns. 2. **Ceftriaxone:** Indicated for *Neisseria gonorrhoeae*, not *C. trachomatis* monotherapy. Used only in dual therapy for co-infection. 3. **Fluoroquinolones:** No longer recommended due to emerging resistance and inferior outcomes. ## Clinical Pearl **Partner notification and treatment:** The sexual partner(s) must be treated empirically with the same regimen (doxycycline 100 mg BD × 7 days) to prevent reinfection, even if asymptomatic. ## Additional Management - Counsel on safe sex practices and barrier contraception. - Repeat NAAT 3 weeks post-treatment only if symptoms persist (test of cure not routinely recommended). - Screen for co-infections: *N. gonorrhoeae*, *Mycoplasma genitalium*, syphilis, HIV. - If pregnant: use azithromycin 1 g single dose (doxycycline contraindicated). [cite:CDC STI Treatment Guidelines 2021; Harrison 21e Ch 181]