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Home > Wellness > Health Library > KOH (Potassium Hydroxide) Test for Thrush
The KOH preparation test is used to
find out 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.
If a person has white patches in the
mouth or on the tongue, a KOH test may be done to find out whether the person
Findings of a KOH test may include the
No yeast or other fungi are present in the sample from the
Yeast or other fungi are present in the sample from the
In general, 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.
Complete the medical test information form (PDF)(What is a PDF document?) to help you prepare for this test.
Current as of:
June 18, 2013
John Pope, MD - Pediatrics & Thomas Emmett Francoeur, MD, MDCM, CSPQ, FRCPC - Pediatrics
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