Utility of Chicago Sky Blue Stain in Rapid Diagnosis of Mycotic Infections

Abstract

Introduction: Diagnosis of fungal infection is mostly relied on clinical skills assisted by array of diagnostic methods. Culture and molecular testing are specific but lacks sensitivity and are labour intensive, time consuming, expensive and not readily available. Direct examination using Potassium Hydroxide (KOH) mount is most often practiced but lacks contrast and requires a skilled eye to interpret. Chicago Sky Blue 6B (CSB) stain has shown a promising result providing coloured contrast and better sensitivity and specificity. Aim: To evaluate the rapid diagnosis of fungal infections using CSB stain over conventional KOH mounts. Materials and Methods: This cross-sectional analytical study was done at RIMS, Raipur catering to rural and tribal population in Chhattisgarh in Central India over a period of 10 months after due approval from Institutional Ethics Committee. Clinically, suspected cases of mycosis belonging to all ages of either gender attending Outpatient Department (OPD) of Dermatology and Ophthalmology Department, who were advised mycological evaluation by physician but not on treatment were included in study. The samples were processed with KOH mount and CSB stain and were observed by two independent observers. The data was managed in Microsoft office Excel and was analysed using tests of proportion and Pearson’s Chi-square test for significance. Results: A total of 128 participants were involved in the study with a male preponderance of 96/128 (75%) as against 32/128 (25%). A total of 110 patients were diagnosed using CSB 6B stain whereas 80 patients were diagnosed using KOH mount. CSB 6B was evaluated against the conventional KOH mount using a Chi-square test and was found to be highly significant with Chi-square value of 39.74 with 1 degree of freedom and p-value of <0.001. Conclusion: This study brought out the significance of CSB 6B stain over conventional KOH mount with better sensitivity, specificity, Negative Predictive Value (NPV) and Positive Predictive Value (PPV) and ease and rapidity of diagnosis with better colour contrast helping clinicians with prompt initiation of treatment with a laboratory confirmation.