Diagnostic value of fungal fluorescence staining on corneal scrapings for fungal keratitis

Abstract

Objective: To analyze the sensitivity and specificity of fungal fluorescent staining in the diagnosis of fungal keratitis, and to compare it with conventional fungal culture, in vivo confocal microscopy (IVCM) and Giemsa staining. To explore its value of clinical application. Methods: Prospective case-control study. A total of 105 consecutive patients (105 eyes) diagnosed with infectious keratitis at Beijing Tongren Hospital from August 2017 to April 2018 were included. Patients with infectious keratitis were divided into fungal keratitis (FK) group and non-fungal keratitis (NFK) group by slit lamp microscopy, corneal in vivo confocal microscopy (IVCM) examination, and the results of Giemsa staining, fluorescent staining and pathogenic culture of corneal scraping from ulcer. The sensitivity and specificity of the above-mentioned examination methods for the diagnosis of fungal keratitis were analyzed. The receiver operating characteristic curve (ROC curve) and Area Under Curve (AUC) values were calculated to determine the diagnostic value of fungal fluorescent staining for fungal keratitis. Results: Among the 105 patients with infectious keratitis, 66 were fungal keratitis, 39 were non-fungal keratitis (29 cases of bacterial keratitis and 10 cases of acanthamoeba keratitis). Isolation from fungal keratitis were mainly Fusarium spp. (43.5%), followed by Alternaria spp. (21.7%) and Aspergillus spp. (19.6%). After fluorescent staining of the ulcer smear, the background of tissue demonstrated homogeneous black or weak blue fluorescence. The cell wall of fungi showed bright blue-violet to blue fluorescence, and the morphology, structure and hyphal density were easily recognized. The sensitivity of different methods for the diagnosis of corneal fungal infection were smear fluorescence staining (97.0%), IVCM (87.9%) , Giemsa staining (86.7%), and fungal culture (69.7%); the specificity of fungal culture was the highest (100%), followed by IVCM and Giemsa staining (94.9%), and fluorescent staining (87.2%). The ascending order of AUC values was: fungal culture (0.848) <Giemsa staining (0.906) <IVCM (0.914) <fluorescence staining (0.921). Conclusion: Fungal fluorescent staining is a rapid and sensitive screening method under microscope with high sensitivity and specificity for the diagnosis of fungal keratitis. It is especially suitable for the diagnosis of patients with low load of hypha or after antifungal therapy. (Chin J Ophthalmol, 2019, 55:601-608).