Comparing Microbiologic Tests for Pathogen Detection in Infectious Keratitis Using Latent Class Analysis

To compare the diagnostic performance of traditional microbiologic tests and next-generation sequencing methods for infectious keratitis pathogen detection.

Participants included 86 subjects diagnosed with acute infectious keratitis at Aravind Eye Hospital in Madurai, India. Corneal scrapings from all subjects were evaluated using Gram stain, potassium hydroxide (KOH) smear, culture, and metagenomic deep sequencing (MDS). The sensitivity and specificity of each test were estimated using latent class analysis.

Among 86 participants, clinical diagnostic tests demonstrated varying sensitivity and specificity for bacterial and fungal keratitis. Gram stain exhibited high sensitivity (89%) and specificity (94%) for bacterial detection, whereas KOH smears showed only moderate sensitivity (75%) and specificity (69%) for fungal detection. Culture testing had lower sensitivity for bacterial (68%) and fungal (56%) identification, but high specificity (92% and 88%, respectively). MDS demonstrated the best balance of sensitivity and specificity across pathogen classes, with 100% sensitivity and 90% specificity for bacterial keratitis and 82% sensitivity with 94% specificity for fungal keratitis. MDS detected critical pathogens missed by culture in 29% of cases, including those whose identification is essential for guiding clinical management and preventing vision-threatening complications.

MDS demonstrated a favorable balance between sensitivity and specificity for both bacterial and fungal keratitis, whereas smears performed well for bacterial but not fungal keratitis and cultures demonstrated high specificity but low sensitivity. Repeated evaluation of diagnostic performance across diverse populations and geographic settings is necessary to validate the reliability and optimize the clinical utility of microbiologic testing for infectious keratitis.