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Austin Nakatsuka, Juan Ortiz, Patricia Chevez-Barrios; A multifaceted diagnostic approach to pathological diagnosis of corneal infection. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3343.
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© ARVO (1962-2015); The Authors (2016-present)
This study was done to evaluate the effectiveness of a multifaceted diagnostic approach of corneal infections, comparing diagnostic techniques including scrape cytology, multiplex PCR and corneal cultures.
We examined corneal washings from 47 eyes obtained from January 2015 to November 2016. Corneal scrapings were obtained and smeared onto glass slides. A swab of lesion was put in universal transport media for viral cultures and cultures plates if needed. One slide of scrapings was stained with PAS, other slides were stained with other special stains depending on PAS findings, and a liquid based cytology (ThinPrep®) and cell block were prepared if transport media was available. Multiplex PCR (targeting HSV-1, HSV-2, VZV, CMV) was performed. Results were compared to culture results.
In 14 cases, culture was determined to be superior to cytology in detection of likely cause of corneal infection. Of these cases, 4 detected Propionibacterium acnes, an organism not detected in cytology. In 23 cases, cytology was superior to culture in the final diagnosis, with 3 cases of Microsporidium detected solely by cytology and 4 of 10 cases of Acanthamoeba detected by cytology with negative cultures. In 8 cases, cytology and cultures correlated in final diagnosis, 1 case was indeterminate, and in 1 case multiplex PCR detected virus not detected on cytology or cultures. Multiplex PCR was performed on 12 cases and was found to be positive in 4 cases, all of which were HSV-1, correlating with cytology findings in 3 of these cases.
A multifaceted diagnostic approach is recommended for accurate diagnosis of corneal infections as some organisms may not be detected by cultures alone. Thus, adequate planning prior to obtaining samples is ideal to minimize false negative results. Culture appears to be superior to cytology in detection of bacterial organisms but other causes of corneal infections, such as Microsporidium and Acanthamoeba, are better detected with cytology. Correlation of cytology and cultures helps to differentiate contaminants from true infective processes. Multiplex PCR from corneal scrapings show good specificity for the targeted organisms, however further studies are required to increase the targeted spectrum. We recommend triaging the sample, aiming to better utilize the amount of tissue obtained including cytopathologic evaluation when possible.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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