Sign in →

Test Code LAB251 KOH Prep


Clinical System Name

KOH Prep Only


Calcofluor Stain

Direct Fungal Exam

Fungal Prep

KOH Exam



Sample Requirements


Hair: Collect several affected hairs including the root, and scrapings from affected area on scalp.

Skin: Obtain skin scrapings from the leading edge of the lesion preferably using a scalpel blade, or alternatively the edge of a microscope slide.

Nails: Clip infected nail, or obtain scrapings from the affected area using a scalpel blade.

Container: Sterile Container

Preferred Vol: N/A

Minimum Vol: N/A

Processing Instructions

CPA: Send sample to Microbiology for processing.  If the sample is shared and only one tube, syringe or other container is received, affix shared sample label and send entire sample plus requisition to Microbiology.


Off-site Children's Lab locations: Send the sample to the SCH Microbiology Laboratory for processing. Sample should be kept at room temperature prior to and during courier transport. 


Other off-site locations: Keep sample at room temperature prior to and during courier transport to the SCH Microbiology Laboratory. 


Temp Time
Room temp 2 hours
Refrigerated N
Frozen N



Procedure Performed Turn Around Time (TAT)
KOH 24/7

24 hours



Performing Laboratory

Seattle Children's Laboratory



Microbiology Laboratory

CPT Codes



This test is not limited to the CPT codes listed.  Others may be added as more testing is necessary and depending on the pathogens isolated (example: MIC's and ID codes)


Includes KOH examination for the presence of yeast or fungal elements. This order does not include a culture for Fungus. See Fungal Culture and KOH Prep or Fungal Culture and KOH Prep for Dermatophytes to request a full culture including a KOH exam. 


Potassium Hydroxide (KOH) digests human tissue cells and helps reveal fungal elements. It is used primarily for hair, skin, and nail samples.


For genital samples, yeast can be easily see on Gram Stain included with Genital Culture. Yeast can also be see on Genital Wet Mount.

Notifiable Result

See Link below for Notifiable Conditions for WA state labs:


See Link below for PDF of phone numbers for Local Health jurisdictions (by County) in WA State:

Reporting Information

Final Report: 24 hours