Dermatology Book


Potassium Hydroxide

Aka: Potassium Hydroxide, KOH Preparation
  1. See Also
    1. Fungal Culture
    2. Onychomycosis
    3. Yeast Vaginitis
    4. Tinea Corporis
    5. Tinea Capitis
  2. Mechanism
    1. KOH dissolves keratin but leaves fungal, hyphae cell wall intact
  3. Preparations: Potassium Hydroxide (KOH) 10-20% solutions
    1. KOH alone
      1. Requires heating (See below)
    2. KOH with Dimethyl Sulfoxide (DMSO) 40% solution
      1. Stable and does not require heating
    3. KOH with Swartz-Medrik Stain
      1. Keratin: Pink
      2. Hyphae: Blue
    4. KOH with Calcofluor White Stain
      1. Used by commercial labs
      2. Binds cellulose and highlights fungal organisms under fluorescent microscopy
  4. Technique: Collect specimen
    1. Skin
      1. Scrape scale with #15 blade or glass slide
    2. Vesicle
      1. Unroof Vesicle and examine roof material on slide
    3. Nail
      1. Scrape keratin debris with #15 or curette
    4. Hair
      1. Remove hairs gently with forceps or
      2. Scrape scale with glass slide or ToothBrush
    5. Vaginal Discharge
      1. See Candida Vulvovaginitis
  5. Technique: Slide Preparation with Potassium Hydroxide (KOH)
    1. Gather the scale into small mound
    2. Add a drop of 10-20% KOH solution
    3. Cover with coverslip
    4. Let slide stand at room Temperature for 5-30 minutes prior to viewing
  6. Technique: Heating
    1. Heat gently until bubbles begin to expand
    2. Heating is not required if KOH preserved with DMSO
  7. Lab: Findings
    1. Images
      1. DermLabKohHyphae.jpg
    2. Low Light and Low power (10x)
      1. Close condenser to its smallest opening
      2. Rack down slightly
      3. Locate piece of scale
        1. Look for branching structures (septate hyphae)
        2. Hyphae are on scale (NOT free floating)
        3. Differentiate from epithelial cell borders
          1. Overlapping cell borders may appear to branch
      4. Focus up and down to examine all levels of specimen
    3. Increase to high power (43x) to confirm yeast or hyphae
  8. Regulations: CLIA
    1. Provider-Performed Microscopy certificate required
  9. References
    1. Hay (2011) J Am Acad Dermatol 65(6): 1219-27 [PubMed]

KOH preparation (C1441630)

Concepts Laboratory Procedure (T059)
LNC LP6358-8
English KOH preparation
Derived from the NIH UMLS (Unified Medical Language System)

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