KOH with Calcofluor White
For the direct microscopic examination of skin scrapings, hairs, nails and other clinical specimens for fungal elements.
This is a very sensitive method, however, a fluorescence microscope with ultraviolet filters is required (Hageage and Harrington, 1984; Hollander et al. 1984; Monheit et al. 1984; Harrington and Hageage 2003).
Solution A Potassium Hydroxide Reagent
- Dissolve the KOH in water and add glycerol.
- Potassium hydroxide 10 g
- Glycerin 10 ml
- Distilled water 80 mL
Solution B Calcofluor White Reagent
- Dissolve Calcofluor white powder in the distilled water by gentle heating.
- Calcofluor white 0.5 g
- Evans blue 0.02 g
- Distilled water 50 mL
Method for Making Microscopic Mounts
- Mix one drop of each solution on the centre of a clean microscope slide.
- Place the specimen in the solution and cover with a coverslip, squash the preparation with the butt of the inoculation needle and then blot off the excess fluid.
- Gently heat the slide and examine microscopically for the presence of fungal elements that fluoresce a chalk-white or brilliant apple green colour, depending on the filters used.
This is a very rapid and sensitive method, however a fluorescence microscope fitted with filters to give an excitation with ultraviolet light below 400 nm wavelength is required.
Hageage and Harrington, Laboratory Medicine 1984,15:109-112