Yeast Identification in Skin by Qualitative Potassium Hydroxide (KOH) Preparation
A microscopy test that examines a skin scraping for yeast, using potassium hydroxide to prepare the sample.
["Yeast seen on this test may support a diagnosis of a superficial fungal skin infection."]
Key facts at a glance
- LOINC
- 55317-2
- Short code
- Yeast Skin Ql KOH Prep
- Synonyms
- Yeast Skin Ql KOH Prep
- Category
- liver
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- — – 500 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- koh-preparation
- CPT
- 84484
- SNOMED
- 302774002
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What is this test?
This test examines a sample taken from the skin for yeast. A potassium hydroxide (KOH) preparation is used to clear skin cells so that yeast or fungal structures can be viewed under a microscope.
Why might I need this test?
It may be ordered when a rash, scaling, redness, or other skin symptoms suggest a fungal infection. The test can help identify yeast such as Candida in skin samples.
How is the test performed?
A clinician scrapes the affected skin or the edge of a lesion and places the material on a laboratory slide. The laboratory adds KOH and examines the preparation under a microscope.
How do I prepare for the test?
No special preparation is usually required. Do not apply creams, ointments, or other skin products to the area immediately before the sample is collected unless your clinician instructs you to do so.
Reference range
Adult: 10-40 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
If yeast is identified, it may indicate a superficial fungal infection, particularly a Candida-related skin infection. Yeast can sometimes exist on the skin without causing symptoms, so the result should be interpreted with the appearance of the rash and other clinical findings. A negative result does not completely exclude a fungal infection if the sample was limited or the infection is deeper in the skin.
Short name
Skin yeast KOH preparation
Frequently asked questions
Does a positive result mean I have a fungal infection?
What is a KOH preparation?
Does the test identify the specific type of yeast?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy