KOH SMEAR
D. M. M. Lab.
KOH Smear
Aim of the test
Treatment of KOH allows rapid observation of fungal elements
because it digests protein debris and clears keratinized tissue so
fungi present in specimen can be seen more readily.
Because of several variable factors, a KOH preparation may not
reveal fungi even when they are present, the collection of the
specimen by the physician, the selection of the portion of the
specimen to be examined by the laboratory, and the size and
number of the organism are extremely important.
The test is useful as a rapid screening a specimen for fungal
elements (hyphae and spores)
Types of Specimen
Superficial Mycoses:
I.
Skin - scrapings collected with either a scalpel or the edge of a
glass slide from the outer area of the lesion. Sent to the laboratory
in folded black paper or any sterile container.
Types of Specimen
Superficial Mycoses:
II.
Hair - specimens scraped from the scalp with a scalpel or hairs
plucked with forceps. Infected hairs are easily removed with their
stubs.
Types of Specimen
Superficial Mycoses:
III. Nail - any damaged, discolored or brittle parts of the nail are
sampled by clipping the full thickness. Where a nail is grossly
thickened scrapings can be taken from underneath the nail to
add to the clippings.
Types of Specimen
Superficial Mycoses:
IV. Mucous membranes - scrapings from the mouth or vagina are
better than swabs if the material is to be processed immediately.
However swabs are commonly used and as yeast’s quickly lose
viability on drying a transport swab is preferred.
Types of Specimen
Subcutaneous Mycoses.
I.
Scrapings/crusts - can be used for microscopy and culture but
bacterial contamination may be a problem. Cleaning of the site
with 70 percent alcohol prior to taking the sample may help.
II.
Pus - should be aspirated and sent with any associated granules
to the laboratory in a sterile container rather than a swab.
III. Biopsy specimens - transported to the laboratory in a sterile
container
Pre Specimen Processing
Specimen collection
See types of specimens
Who will collect the specimen
Depending on the type of the specimen
Quantity of specimen
See types of specimens
Time relapse before processing the sample
As soon as possible to prevent overgrowth of contaminating
bacteria or fungi, and storage at room temperature.
Specimen Processing
Procedure:
1. Place a drop of (10-20)% KOH in the center of a clean
microscopic slide.
2. Place a fragment of tissue, purulent materials or scraping in KOH
drop.
3. Tease the materials well enough with corner of a coverslip to give
a thin preparation or break up the materials with a sterile loop.
4. Mount with coverslip.
5. Allow preparation to digest for approximately 10 minutes or longer
depending on the tested materials.
Procedure continue …..
6. Gently warm the slide (do not overheat) Gently press on the slide
to help disperse tissue materials.
7. Screen under low power objective,
8. Then Use high (40 X) power magnification to verify the presence
of fungal elements.
Hyphae
Hyphae
Mycelium
Yeast
Yeast
Post Specimen Processing
Result reporting:
Report any fungal element (Description of the hyphae is important,
e.g. septated or non septated)
Turn around time:
The results is expected 2 hours after specimen reception.