KOH test

<h2 id="procedure">Procedure</h2>
<p>The KOH test for fungus is conducted on an outpatient basis and patients do not need to prepare in advance.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
Results are usually available while the patient waits or the next day if sent to a <a href="/facts/Clinical_laboratory/ov10GjQD">clinical laboratory</a>. 
The KOH test procedure may be performed by a <a href="/facts/Physician/qJ3woFvG">physician</a>, <a href="/facts/Nurse_practitioner/GGINrFkT">nurse practitioner</a>, physician associate, medical assistant, nurse, midwife<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> or medical laboratory technician. If fungal cultures are required, the test is performed by a technologist who specializes in microbiology.
</p>
<ol><li>Collection: Skin, nail, or hair samples are collected from the infected area on the patient.  For skin samples, a scalpel or edge of a glass slide is used to gently scrape skin scales from the infected area.  For hair samples, a forceps is used to remove hair shafts and follicles from the infected site.  If the test is being sent to a laboratory, the scrapings are placed in a sterile covered container.</li>
<li>The scrapings are placed directly onto a microscope slide and are covered with 10% or 20% potassium hydroxide.</li>
<li>The slide is left to stand until clear, normally between five and fifteen minutes, in order to dissolve skin cells, hair, and debris.</li>
<li>To enhance clearing <a href="/facts/Dimethyl_sulfoxide/T4HSYfuC">dimethyl sulfoxide</a> can be added to the slide.  To make the fungi easier to see lactophenol cotton blue <a href="/facts/Stain/7VhlycN8">stain</a> can be added.</li>
<li>The slide is gently heated to speed up the action of the KOH.</li>
<li>Adding <a href="/facts/Calcofluor-white/IH8WU0Q8">calcofluor-white</a> stain to the slide will cause the fungi to become fluorescent, making them easier to identify under a <a href="/facts/Fluorescence_microscope/eMwIdrRR">fluorescence microscope</a>.</li>
<li>Place the slide under a microscope to read.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a></li></ol>
<h2 id="evaluation">Evaluation</h2>
<p>Dermatophytes are easily recognized under the microscope by their long branch-like tubular structures called <a href="/facts/Hyphae/xogd3AHz">hyphae</a>. Fungi causing <a href="/facts/Ringworm/hFyb8T6n">ringworm</a> infections produce septate (segmented) hyphae. Some show the presence of <a href="/facts/Spore/6qDRdcrs">spores</a> formed directly from the hyphae (arthroconidia). Under the microscope <a href="/facts/Tinea_versicolor/y4wzgMrl">Tinea versicolor</a> is recognized by curved hyphae and round yeast forms that give it a spaghetti-and-meatball appearance.
Yeast cells appear round or oval and budding forms may be seen. The KOH prep cannot identify the specific organism; the specimen can be submitted for fungal culture to identify the organism.
</p><p>A normal, or negative, KOH test shows no fungi (no dermatophytes or yeast). Dermatophytes or yeast seen on a KOH test indicate the person has a fungal infection. Follow-up tests are usually unnecessary.
</p><p>The skin may be sore after the test because of the tissue being scraped off the top of the surface of the skin.
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<h2 id="external-links">External links</h2>
<ul><li><a href="http://medical-dictionary.thefreedictionary.com/KOH+Test">Medical-dictionary.thefreedictionary.com</a></li>
<li><a href="http://www.medicalhealthtests.com/articles/233/medical-tests/koh-test-for-candida-albicans.html">Medicalhealthtests.com</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>MedlinePlus Encyclopedia: Skin lesion KOH exam <a href="/wiki/MedlinePlus" target="_blank">/wiki/MedlinePlus</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Birnbaum, PS (May 1985). "Cost containment: freestanding emergency centers and the emergency department". The American Journal of Emergency Medicine. 3 (3): 259. doi:10.1016/0735-6757(85)90105-6. PMID 3994805. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>"R.R.O. 1990, Reg. 682: LABORATORIES". Government of Ontario. 2014-07-24. Retrieved March 4, 2017. <a href="https://www.ontario.ca/laws/regulation/900682" target="_blank">https://www.ontario.ca/laws/regulation/900682</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Frances Talaska Fischbach; Marshall Barnett Dunning (2004). A manual of laboratory and diagnostic tests. Williams & Wilkins. ISBN 0781741807.[page needed] <a href="0781741807" target="_blank">0781741807</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
</ol>

KOH test open-in-new

KOH test