KOH mount for superficial fungal infections using cellophane tape: Comparison with standard technique

Introduction

Whenever fungal infection is suspected it is prudent to perform a KOH mount and if possible culture for fungus to confirm the diagnosis. Scraping of skin is usually taken with a pre- flamed blunt scalpel from the edge of the lesion. Scrapings may be collected in a black paper or directly on to the slide. 10% KOH is added to the collected material, covered by a cover slip made of fragile glass and gently preheated before examining for fungus. Special transport packs backed by black card when available can be used to transport the scrapings.[1] Sampling can be done using vinyl adhesive tape,[2] or microscopic slides.[3],[4] We report a simple method to collect samples from the affected site and also to examine the specimen under KOH mount.

Materials and Methods

Nine patients with tinea versicolor and 6 with dermatophytic infection were studied. Scraping and KOH mount by standard method were done in all the patients.[1] The same patients were also studied by the modified method as follows; A 5cm long and 2 cm wide scotch tape (transparent cellophane tape) was applied over the affected site, pressed firmly and removed. The tape was then stuck on the surface of the glass slide and sent to the laboratory, where the tape was gently lifted and replaced after placing 3 to 4 drops of 10% KOH solution. The undersurface of the slide was gently warmed and examined under microscope. In addition we folded the tape after stripping the horny layer by bringing the adhesive surfaces together. The folded tape was sent to the laboratory where it was re-opened and mounted with KOH as described above. To enable easy separation of the folded tape tiny bit of paper was attached to each end. The paper was also useful to label the specimen for identification.

Results

Fungal hyphae were detected by both the methods in all the 15 cases. Fungal elements could also be demonstrated after unfolding by separating the adhesive surface of tape and mounting it with KOH.

Discussion

The clinical diagnosis of fungal infection is confirmed by simple KOH mount. The modified technique of using vinyl plastic tape for stripping horny layer and mounting with KOH has been advocated.[2] We compared the strip (cellophane tape) method with the direct KOH technique. Standard method for KOH mount is time taking and relatively more difficult than the method herein described. Moreover the fungal hyphae were better demonstrated by the tape technique than direct KOH mount. The further modification by bringing the adhesive surfaces together can be used for easy collection and transport of the specimen and avoid using transport packs such as black card. The main draw back is that this method is not useful for collecting specimens from the macerated skin and nail.