The incidence of fungal keratitis in Zagazig University Hospitals, Egypt and the value of direct microscopy and PCR technique in rapid diagnosis

Objective: To determine the frequency and risk factors of fungal keratitis (FK) and the value of direct microscopy and PCR techniques of corneal smears as appropriate diagnostic methods. Methods: The keratitis cases in Ophthalmology Department of Zagazig University Hospitals, between January and June 2012 were enrolled. Corneal samples were examined by direct microscopic examination of wet mount preparation with KOH (10%), PCR technique and cultured simultaneously. The corneal smear and PCR findings were compared to the culture results to analyze specificity, sensitivity and predictive values of these techniques. Results: A total of 350 patients diagnosed as keratitis and 60 of them were included in the study by a systemic random sampling method. The FK was proven in 33 (55%) cases with culture results. Ocular trauma (63.6%) was the most prevalent predisposing factor. The cultures revealed that the most frequent fungal pathogen were Penicillium spp. (24.2%) followed by Aspergillus fumigatus (21.2%). Direct microscopic examination had a sensitivity of 100%, specificity of 66.7%, a positive predictive value (PPV) of 78.6% and a negative predictive value (NPV) of 100%. PCR had a sensitivity of 100%, specificity of 88.9%, a PPV of 91.7% and a NPV of 100%. Conclusion: Although, PCR is able to detect fungi in a high proportion of culture negative cases, it is difficult to be used as a routine diagnostic test due to the economic reasons. Therefore, we strongly recommend the use of direct microscopy of corneal smear as a rapid, economic and sensitive method for screening of FK.