How is Chlamydia trachomatis ocular infection typically diagnosed?

• A. Nucleic acid amplification testing (NAAT) of ocular swab or conjunctival sample; serology may support but NAAT is preferred
• B. Gram stain showing intracellular Gram-negative diplococci
• C. Viral culture
• D. Fungal culture

Answer: (A)

Detecting the organism directly from the eye using nucleic acid amplification testing (NAAT) on an ocular swab or conjunctival sample is the best way to diagnose ocular Chlamydia trachomatis infection. NAATs target chlamydial DNA or RNA, offering high sensitivity and specificity and working well with small conjunctival specimens to provide rapid, accurate results that guide treatment. Serology can support exposure history but cannot reliably distinguish active ocular infection from past exposure, so it isn’t the primary diagnostic tool. Gram stain is not reliable for Chlamydia because the organism isn’t readily detected that way in routine conjunctival samples, and finding intracellular Gram-negative diplococci would suggest Neisseria gonorrhoeae rather than Chlamydia. Viral and fungal cultures target other pathogens and do not diagnose chlamydial conjunctivitis.