Efficacy of in-house fluorescent stain for fungus

Abstract

Context: Mycotic infections are gaining importance in the present day medicine, and definite demonstration of fungus is essential for diagnosis. Small numbers of organisms in the smear can be identified by fluorescence microscopy. Calcofluor white (CFW) fluorescent stain is a textile brightener mixed with Evans blue. It is expensive and not easily available. Aims: (1) To assess the efficacy of in-house CFW fluorescent stain for fungus in relation to conventional CFW stain, histopathology, and culture. (2) To determine sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) with culture as gold standard. Settings and Design: One hundred cases of suspected dermatophytosis and 15 cases of systemic mycosis were included in the study. Subjects and Methods: The local whitener Ranipal is added with Robin blue, another brightener, and was used to stain teased fungal cultures. Skin, hair, and nails require pretreatment with potassium hydroxide (KOH). Biopsy slides require deparaffinization and pretreatment with KOH before staining. Conventional calcofluor stain, histopathology, and culture were done. Statistical Analysis Used: Statistical analysis was performed using sensitivity, specificity, NPV, and PPV. Results: The results are consistently comparable with conventional stain. The sensitivity was 100%, specificity was 93.3%, NPV was 100%, and PPV was 85.7%. It is also cost effective when compared to commercial stains. Conclusions: In-house stain can be used for screening of fungus in direct samples, biopsies as alternative in resource-constrained laboratories.

Keywords

• Calcofluor
• fluorescent
• fungal stain