Sensitivity and Specificity of Potassium Hydroxide Smears of Skin Scrapings for the Diagnosis of Tinea Pedis

Abstract

To the Editor.— The use of potassium hydroxide to visualize fungi in microscopic preparations of skin, hair, and nail scrapings is a rapid, inexpensive, and easy procedure.1Little has been written about its sensitivity and specificity for detecting tinea pedis. We conducted a prospective analysis of the potassium hydroxide preparation of skin scrapings from patients seen by a group of five dermatologists for the diagnosis of superficial fungal infections of the foot. Subjects and Methods.— No patient had been using topical or systemic antifungal therapy for at least 1 month prior to the study. Each patient had the suspicious area scraped with the edge of a scalpel blade, with scrapings sandwiched between two glass slides, taped, and sent to the laboratory within 24 hours for analysis. Skin scrapings were inoculated onto three different growth media, and microscopy was performed with potassium hydroxide (10% [weight per volume] solution, with