Key points Can microbial keratitis caused by Aspergillus species be diagnosed using a rapid lateral flow device (LFD) from corneal scraping samples and a minimally invasive corneal swab sampling technique? Findings In this diagnostic study of 198 participants in southern India from whom scrape and swab samples were collected, high sensitivity and high specificity were achieved with a rapid lateral flow device (LFD) identifying Aspergillus species . Meaning The findings of this study suggest that a commercially available rapid lateral flow device (LFD) coupled with customized ratiometric analysis has high diagnostic accuracy and could be an alternative standard of care for point-of-care diagnosis of microbial keratitis. |
Importance
Microbial keratitis ( MK) is a common cause of unilateral visual impairment, blindness, and eye loss in low- and middle-income countries. There is an urgent need to develop and implement rapid and simple point-of-care diagnostics for MK to increase the likelihood of good outcomes.
Aim
To evaluate the diagnostic performance of the Aspergillus-specific lateral flow device (AspLFD) for identifying Aspergillus species causing microbial keratitis (MK) in corneal scraping and swab specimens from patients presenting with microbial keratitis.
Design, environment and participants
This diagnostic study was performed between May 2022 and January 2023 at the corneal clinic of Aravind Eye Hospital in Madurai, Tamil Nadu, India.
All study participants were recruited during their first clinic presentation. Patients aged 15 years or older met eligibility criteria if they attended their first appointment, had a corneal ulcer suggestive of a bacterial or fungal infection, and were about to undergo a diagnostic scraping and culture.
Main results and measures
Sensitivity and specificity of the Aspergillus-specific lateral flow device (AspLFD) with corneal samples collected from patients with microbial keratitis (MK). During routine diagnostic scraping, a minimally invasive corneal swab and an additional corneal scraping were collected and transferred to aliquots of sample buffer and analyzed using a lateral flow device (LFD) if the patient met the inclusion criteria. .
Photographs of devices were taken with a smartphone and analyzed using a ratiometric approach developed for this study. AspLFD results were compared with culture reports.
Results
The 198 participants who met inclusion criteria had a mean (range) age of 51 (15-85) years and included 126 men (63.6%). Overall, 35 of 198 participants with corneal scrapings (17.7%) and 17 of 40 participants with swab samples (42.5%) had positive culture results for Aspergillus species .
The results of radiometric analysis for scraping samples found that AspLFD achieved high sensitivity (0.89; 95% CI, 0.74-0.95), high negative predictive value (0.97; 95% CI, %, 0.94-0.99), a low negative likelihood ratio (0.12; 95% CI, 0.05-0.30), and a precision of 0.94 (95% CI, 0.90-0.99). 0.97).
The results of radiometric analysis for swab samples showed that AspLFD had high sensitivity (0.94; 95% CI, 0.73-1.00), high negative predictive value (0.95; 95% CI, %, 0.76-1.00), a low negative likelihood ratio (0.07; 95% CI, 0.01-0.48), and a precision of 0.88 (95% CI, 0.73-0.48). 0.96).
Conclusions and relevance The results of this diagnostic study suggest that AspLFD, together with the lateral flow device (LFD) ratiometric analysis developed for this study, has high diagnostic accuracy in the identification of Aspergillus species from corneal scrapings and swabs. This technology is an important step towards providing point-of-care diagnostics for MK and could inform clinical management strategy. |
