A rapid lateral-flow device shows high sensitivity and specificity in identifying Aspergillus species in corneal samples, aiding in diagnosing microbial keratitis. The device, coupled with ratiometric analysis, proves robust and cost-effective, potentially revolutionizing MK diagnosis, especially in low-resource settings
A commercially available rapid lateral-flow device showed high sensitivity and specificity for identifying Aspergillus species from corneal scrapes and swabs obtained from patients presenting with bacterial or fungal infection,1 according to the lead study author Rameshkumar Gunasekaran, MSc, from the Department of Ocular Microbiology, Aravind Eye Hospital and Postgraduate Institute of Ophthalmology, Madurai, Tamil Nadu, India.
Development of a rapid and simple diagnostic device for microbial keratitis (MK) would be a major step forward in patient care because of the commonly occurring devastating loss of vision and potential eye loss resulting from MK 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,” the authors commented.
The investigators conducted a diagnostic study between May 2022 and January 2023 at the corneal clinic of Aravind Eye Hospital. All study participants aged 15 years and older were recruited during their first presentation to the clinic, had a corneal ulcer that was considered a bacterial or fungal infection, and were about to undergo a diagnostic scrape and culture.
The investigators determined the sensitivity and specificity of the Aspergillus-specific lateral-flow device with corneal samples collected from patients with MK. During routine scraping, the investigators used a minimally invasive corneal swab and collected an additional corneal scrape that were transferred to aliquots of sample buffer and analyzed by the lateral-flow device. Photographs of the devices were taken with a smartphone and analyzed using a ratiometric approach, which was developed for this study. The results obtained using the lateral-flow device then were compared with culture results, they reported.
A total of 198 participants (126 males; mean age, 51 years; range, 15-85 years) were included.
The authors reported that 35 of the 198 participants with corneal scrape (17.7%) and 17 of 40 participants with swab samples (42.5%) had positive culture results for Aspergillus species.
The ratiometric analysis results obtained for the scrape samples showed that the lateral-flow device achieved high sensitivity (0.89; 95% confidence interval [CI], 0.74-0.95), high negative predictive value (0.97; 95% CI, 0.94-0.99), low negative likelihood ratio (0.12; 95% CI, 0.05-0.30), and an accuracy of 0.94 (95% CI, 0.90-0.97).
The ratiometric analysis results for the swab samples indicated that the lateral-flow device had high sensitivity (0.94; 95% CI, 0.73-1.00), high negative predictive value (0.95; 95% CI, 0.76-1.00), low negative likelihood ratio (0.07; 95% CI, 0.01-0.48), and an accuracy of 0.88 (95% CI, 0.73-0.96).
In commenting on the findings, the authors pointed out the importance of this technology for providing point-of-care diagnostics for MD.
They commented, “Accurate and early diagnosis of MK is essential to rationally initiate clinical management and improve patient outcomes. Point-of-care diagnostics have revolutionized disease management for a number of conditions but are lacking for MK. Lateral-flow devices are low cost and simple to use. The [device] used in this study, coupled with the simple bespoke ratiometric analysis, proved to be a robust, highly sensitive and specific tool for identifying Aspergillus species from scrape and swab samples. This diagnostic feasibility study suggests that the lateral-flow device technology could offer an alternative gold standard approach for the diagnosis of MK (and enable MK diagnosis at the primary care level for the first time), particularly if multiplexed lateral-flow device are developed to simultaneously screen several important MK pathogens.”