Accuracy of interpretation of fungi by direct microscopy using chlorazol black e versus gold standard potassium Hydroxide

Abstract

Background: Superficial fungal infections are skin diseases that affect people worldwide. To confirm the diagnosis of these diseases, mycological investigation by direct microscopic examination and culture are required. Chlorazol black E (CBE) is an acid-based dye of the trisazo group of dyes that has a high affinity for chitin. Data specific to the efficacy of CBE for detection of fungi by direct microscopy is limited. Objective: To investigate the accuracy of interpretation of fungi by direct microscopy using CBE versus potassium hydroxide (KOH). Materials and Methods: The present study was a retrospective study, conducted at the Department of Dermatology, Faculty of Medicine, Siriraj Hospital, Mahidol University in 2018. Slide interpretations by 33 microscopists were reviewed. The interpretation scores of all participants in each specimen were recorded and compared between CBE and KOH. Results: Thirty-three participants were included. The mean interpretation score of all participants was 17.2±4.9. The mean interpretation scores of overall specimens using CBE was significantly more than using KOH (p<0.001). For Candida spp. and dermatophytes, the accuracy of interpretation using CBE was statistically higher than KOH (p=0.020, p<0.001, respectively). Relative to negative findings, CBE yielded significantly more false-positive results than KOH (p=0.003). Conclusion: CBE for direct microscopic examination of fungi specimens is helpful for increasing the accuracy of interpretation. However, false-positive results are more prevalent when using CBE.