MicrobiologyDermatology

KOH Mount

Normal Range
Negative for fungal elements
Sample Type
Skin scraping, Hair, or Nail clipping
Fasting
No
Unit
Qualitative

Function

The Potassium Hydroxide (KOH) Mount is a rapid bedside or laboratory test used to identify fungal infections of the skin, hair, and nails. KOH is a strong alkali; when applied to a clinical sample, it dissolves keratin and cellular debris, leaving the sturdy chitinous cell walls of fungi intact and visible under a microscope.

Why it is Ordered

This test is ordered when a patient presents with itchy, scaly, or discolored skin patches, brittle nails, or unexplained hair loss. It helps clinicians differentiate between fungal infections (like ringworm or yeast infections) and other skin conditions like psoriasis or eczema, which may look similar but require vastly different treatments.

Associated Conditions

  • Dermatophytosis (Tinea): Includes athlete’s foot (tinea pedis), jock itch (tinea cruris), and ringworm of the body (tinea corporis).
  • Candidiasis: Yeast infections caused by Candida species, often occurring in moist skin folds.
  • Tinea Versicolor: A common fungal infection that causes small, discolored patches of skin.
  • Onychomycosis: Fungal infection of the fingernails or toenails, causing thickening and yellowing.

Why Context Matters

The accuracy of a KOH mount is highly dependent on the quality of the specimen collection and the experience of the microscopist. A 'false negative' can occur if not enough skin scales were scraped or if the patient recently applied antifungal creams to the area. If symptoms persist despite a negative result, a second opinion involving a fungal culture or a skin biopsy may be necessary for a definitive diagnosis.

Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.

Clinical References

Source-of-truth databases and clinical guidelines for KOH Mount:

Research & Guidelines

Related Indicators

Albert's Stain

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Spore Stain

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AFB Culture (Radiometric)

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DR

Medically Reviewed by Dr. Binoy Babu, MBBS

Board Certified Doctor • 10+ Years Clinical Experience

Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.

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