In a woman with suspected PID, which investigation is most appropriate to detect Chlamydia trachomatis and Mycoplasma genitalium?

Answer: B. Nucleic acid amplification test (NAAT)

Microbiological investigation of PID

The NAAT (nucleic acid amplification test) is the investigation of choice for Chlamydia trachomatis and Mycoplasma genitalium.

Full investigation set

• NAAT - chlamydia and M. genitalium.
• Endocervical specimen - inflammatory cells and Neisseria gonorrhoeae.
• Microscopy of Gram-stained vaginal discharge - for bacterial vaginosis.
• Pregnancy test - to exclude ectopic pregnancy.
• Inflammatory markers (raised WBC, ESR, CRP - non-specific), urine analysis if UTI suspected, and screening for other STIs.

Why the others are wrong

Blood culture, ESR (non-specific), abdominal X-ray and CA-125 do not specifically detect chlamydia or M. genitalium; the NAAT is the targeted test.