Exam Overview
The KOH preparation test is used to determine whether oral candidiasis (thrush) is present in a person's mouth. A sample of skin is taken from the person's mouth by lightly scraping the white patches.
The sample is then placed on a slide with potassium hydroxide (KOH) solution and gently heated. This solution slowly dissolves the skin cells but not the yeast cells. The yeast cells can then be seen with a microscope. Color stains may be used so that the yeast cells are easier to see.
Why It Is Done
If a person has white patches in the mouth or on the tongue, a KOH test may be done to determine whether the person has thrush.
Results
Findings of a KOH test may include the following.
Normal
No yeast or other fungi are present in the sample from the person's mouth.
Abnormal
Yeast or other fungi are present in the sample from the person's mouth.
What To Think About
Generally, a KOH test is not needed to diagnose thrush. A doctor usually can diagnose thrush by looking at the white patches in a person's mouth. But if thrush does not respond to prescribed medicines, a KOH test may be done to determine whether drug-resistant strains of yeast are causing the infection.
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Credits
| Author | Maria G. Essig, MS, ELS |
| Editor | Susan Van Houten, RN, BSN, MBA |
| Associate Editor | Pat Truman, MATC |
| Primary Medical Reviewer | Michael J. Sexton, MD - Pediatrics |
| Specialist Medical Reviewer | Thomas Emmett Francoeur, MDCM, CSPQ, FRCPC - Pediatrics |
| Last Updated | March 10, 2008 |
