II. Mechanism
- KOH dissolves keratin but leaves fungal, hyphae cell wall intact
III. Preparations: Potassium Hydroxide (KOH) 10-20% solutions
- KOH alone
- Requires heating (See below)
- KOH with Dimethyl Sulfoxide (DMSO) 40% solution
- Stable and does not require heating
- KOH with Swartz-Medrik Stain
- Keratin: Pink
- Hyphae: Blue
- KOH with Calcofluor White Stain
- Used by commercial labs
- Binds cellulose and highlights fungal organisms under fluorescent microscopy
IV. Technique: Collect specimen
- Skin
- Scrape scale with #15 blade or glass slide
-
Vesicle
- Unroof Vesicle and examine roof material on slide
- Nail
- Scrape keratin debris with #15 or curette
-
Hair
- Remove hairs gently with forceps or
- Scrape scale with glass slide or ToothBrush
- Vaginal Discharge
V. Technique: Slide Preparation with Potassium Hydroxide (KOH)
- Gather the scale into small mound
- Add a drop of 10-20% KOH solution
- Cover with coverslip
- Let slide stand at room Temperature for 5-30 minutes prior to viewing
VI. Technique: Heating
- Heat gently until bubbles begin to expand
- Heating is not required if KOH preserved with DMSO
VII. Lab: Findings
- Images
- Low Light and Low power (10x)
- Close condenser to its smallest opening
- Rack down slightly
- Locate piece of scale
- Look for branching structures (septate hyphae)
- Hyphae are on scale (NOT free floating)
- Differentiate from epithelial cell borders
- Overlapping cell borders may appear to branch
- Focus up and down to examine all levels of specimen
- Increase to high power (43x) to confirm yeast or hyphae
VIII. Regulations: CLIA
- Provider-Performed Microscopy certificate required