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Aims |
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Conventional potassium hydroxide (KOH) wet mount microscopy is used for the diagnosis of dermatomycosis. However, KOH poorly differentiates fungal elements from skin cells, and is time-consuming. This study evaluated the performance of a contrast stain against standard KOH microscopy, measuring: 1) diagnostic sensitivity, 2) microscopic time taken to read and report, and 3) impact of prior microscopy experience. |
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Methods |
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293 skin scrapings and nail clippings from patients with suspected dermatophyte infections were used in this study. Microscopic examination (ME) was first performed using KOH. Slides were then counterstained using Chicago Sky Blue (CSB) and re-examined by a separate technologist. Detection of fungal elements by either method was taken as true positive. ME reading time was recorded using a stopwatch. |
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Results |
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Fungal elements were detected in 88 (30%) samples, with 100% diagnostic sensitivity for CSB compared with 88.9% for KOH. When considering all tested samples, ME reading times were slightly faster for CSB (mean 4.7s, median -13s). 155 (53%) samples involved MEs where the CSB was read by a junior technologist, and KOH by a senior technologist. For positive samples, ME reading times were faster for CSB (79.6% of samples). Conversely for negative samples, ME reading times were faster for KOH (67% of samples). 133 (45.4%) samples were examined by technologists of the same seniority. ME reading times for CSB were faster for both positive samples (69.2% of samples) and negative samples (72.3% of samples). |
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Conclusions |
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CSB is superior to KOH both in terms of diagnostic sensitivity and ME reading times. When reader experience is disregarded, CSB ME yields faster average time compared to KOH ME. |