Athlete's foot laboratory findings: Difference between revisions
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==Overview== | ==Overview== | ||
Athlete's foot can usually be diagnosed by visual inspection of the skin, but where the diagnosis is in doubt direct [[microscopy]] of a potassium hydroxide preparation (known as a [[KOH test]]).<ref name=Palacio2000>{{cite journal |last=del Palacio |first=Amalia |authorlink= | coauthors=Margarita Garau, Alba Gonzalez-Escalada and Mª Teresa Calvo |title=Trends in the treatment of dermatophytosis | journal=Biology of Dermatophytes and other Keratinophilic Fungi |volume= |issue= |pages=148–158 |date= |url=http://www.dermatophytes.reviberoammicol.com/p148158.pdf |format=PDF|doi= |id= |accessdate=2007-10-10}}</ref> A KOH preparation is performed on skin scrapings from the affected area. The KOH preparation has an excellent positive predictive value, but occasionally [[false negative]] results may be obtained, especially if treatment with an anti-fungal medication has already begun. | |||
* Athlete's foot can usually be diagnosed by visual inspection of the skin, but where the diagnosis is in doubt direct [[microscopy]] of a [[potassium hydroxide]] preparation (known as a [[KOH test]]).<ref name="Palacio2000">{{cite journal |last=del Palacio |first=Amalia |authorlink= | coauthors=Margarita Garau, Alba Gonzalez-Escalada and Mª Teresa Calvo |title=Trends in the treatment of dermatophytosis | journal=Biology of Dermatophytes and other Keratinophilic Fungi |volume= |issue= |pages=148–158 |date= |url=http://www.dermatophytes.reviberoammicol.com/p148158.pdf |format=PDF|doi= |id= |accessdate=2007-10-10}}</ref> | |||
* A KOH preparation is performed on skin scrapings from the affected area. | |||
* The KOH preparation has an excellent [[positive predictive value]], but occasionally [[false negative]] results may be obtained, especially if treatment with an anti-fungal medication has already begun. | |||
==Laboratory Findings== | ==Laboratory Findings== | ||
===Microscopy=== | ===Microscopy=== | ||
*Skin scrapings from affected areas of toes, web spaces, | *Skin scrapings from affected areas of [[Toe|toes]], web spaces, [[Sole (foot)|sole]]<nowiki/>s including scales can be taken.<ref name="pmid25176455">{{cite journal| author=Nenoff P, Krüger C, Schaller J, Ginter-Hanselmayer G, Schulte-Beerbühl R, Tietz HJ| title=Mycology - an update part 2: dermatomycoses: clinical picture and diagnostics. | journal=J Dtsch Dermatol Ges | year= 2014 | volume= 12 | issue= 9 | pages= 749-77 | pmid=25176455 | doi=10.1111/ddg.12420 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=25176455 }} </ref> | ||
*Scrapings are stained with KOH and viewed under a microscope. | *To diagnose vesicular tinea pedis, the entire roof of the bulla is removed and mounted for a high yield of fungus. | ||
* | *Scrapings are stained with [[Potassium hydroxide|KOH]] and viewed under a microscope. | ||
*Dimethyl sulfoxide may be used to dissolve keratin in the scrapings. | *Counterstains may be used to better visualize the fungus such as chorazol black which is specific for [[chitin]]. | ||
*[[Dimethyl sulfoxide]] may be used to dissolve [[keratin]] in the scrapings. | |||
===Biopsy=== | ===Biopsy=== | ||
* A [[biopsy]] of the affected skin (i.e. a sample of the living skin tissue) can be taken for [[histological]] examination. | * A [[biopsy]] of the affected skin (i.e. a sample of the living skin tissue) can be taken for [[histological]] examination. | ||
===Culture=== | ===Culture=== | ||
*A culture is usually done to identify the dermatophyte species. | *A [[Culture collection|culture]] is usually done to identify the [[dermatophyte]] species. | ||
*Mycobiotic agar, dermatophyte test medium, Sabouraud's agar etc are used as culture medium.<ref name="pmid12956194">{{cite journal| author=Gupta AK, Chaudhry M, Elewski B| title=Tinea corporis, tinea cruris, tinea nigra, and piedra. | journal=Dermatol Clin | year= 2003 | volume= 21 | issue= 3 | pages= 395-400, v | pmid=12956194 | doi=10.1016/s0733-8635(03)00031-7 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12956194 }} </ref> | *Mycobiotic agar, dermatophyte test medium, Sabouraud's agar etc are used as [[Growth medium|culture medium]].<ref name="pmid12956194">{{cite journal| author=Gupta AK, Chaudhry M, Elewski B| title=Tinea corporis, tinea cruris, tinea nigra, and piedra. | journal=Dermatol Clin | year= 2003 | volume= 21 | issue= 3 | pages= 395-400, v | pmid=12956194 | doi=10.1016/s0733-8635(03)00031-7 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12956194 }} </ref> | ||
===Immunochromatography=== | ===Immunochromatography=== | ||
*Immunochromatography kits use a solution to extract dermatophyte antigens from a tissue sample and detect their reaction with monoclonal antibodies to these antigens.<ref name="pmid28566667">{{cite journal| author=Tsunemi Y| title=Dermatophyte Antigen Kit. | journal=Med Mycol J | year= 2017 | volume= 58 | issue= 2 | pages= J51-J54 | pmid=28566667 | doi=10.3314/mmj.17.005 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=28566667 }} </ref> | *Immunochromatography kits use a solution to extract dermatophyte [[Antigen|antigens]] from a tissue sample and detect their reaction with [[monoclonal antibodies]] to these antigens.<ref name="pmid28566667">{{cite journal| author=Tsunemi Y| title=Dermatophyte Antigen Kit. | journal=Med Mycol J | year= 2017 | volume= 58 | issue= 2 | pages= J51-J54 | pmid=28566667 | doi=10.3314/mmj.17.005 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=28566667 }} </ref> | ||
*This method is effective for tinea unguium but not for tinea pedis. | *This method is effective for [[tinea unguium]] but not very effective for tinea pedis. | ||
*Samples that test positive with this method are re-examined using microscopy or culture methods to make a final diagnosis. | *Samples that test positive with this method are re-examined using microscopy or culture methods to make a final diagnosis. | ||
Latest revision as of 18:39, 27 July 2020
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sanjana Nethagani, M.B.B.S.[2]
Overview
- Athlete's foot can usually be diagnosed by visual inspection of the skin, but where the diagnosis is in doubt direct microscopy of a potassium hydroxide preparation (known as a KOH test).[1]
- A KOH preparation is performed on skin scrapings from the affected area.
- The KOH preparation has an excellent positive predictive value, but occasionally false negative results may be obtained, especially if treatment with an anti-fungal medication has already begun.
Laboratory Findings
Microscopy
- Skin scrapings from affected areas of toes, web spaces, soles including scales can be taken.[2]
- To diagnose vesicular tinea pedis, the entire roof of the bulla is removed and mounted for a high yield of fungus.
- Scrapings are stained with KOH and viewed under a microscope.
- Counterstains may be used to better visualize the fungus such as chorazol black which is specific for chitin.
- Dimethyl sulfoxide may be used to dissolve keratin in the scrapings.
Biopsy
- A biopsy of the affected skin (i.e. a sample of the living skin tissue) can be taken for histological examination.
Culture
- A culture is usually done to identify the dermatophyte species.
- Mycobiotic agar, dermatophyte test medium, Sabouraud's agar etc are used as culture medium.[3]
Immunochromatography
- Immunochromatography kits use a solution to extract dermatophyte antigens from a tissue sample and detect their reaction with monoclonal antibodies to these antigens.[4]
- This method is effective for tinea unguium but not very effective for tinea pedis.
- Samples that test positive with this method are re-examined using microscopy or culture methods to make a final diagnosis.
References
- ↑ del Palacio, Amalia. "Trends in the treatment of dermatophytosis" (PDF). Biology of Dermatophytes and other Keratinophilic Fungi: 148–158. Retrieved 2007-10-10. Unknown parameter
|coauthors=ignored (help) - ↑ Nenoff P, Krüger C, Schaller J, Ginter-Hanselmayer G, Schulte-Beerbühl R, Tietz HJ (2014). "Mycology - an update part 2: dermatomycoses: clinical picture and diagnostics". J Dtsch Dermatol Ges. 12 (9): 749–77. doi:10.1111/ddg.12420. PMID 25176455.
- ↑ Gupta AK, Chaudhry M, Elewski B (2003). "Tinea corporis, tinea cruris, tinea nigra, and piedra". Dermatol Clin. 21 (3): 395–400, v. doi:10.1016/s0733-8635(03)00031-7. PMID 12956194.
- ↑ Tsunemi Y (2017). "Dermatophyte Antigen Kit". Med Mycol J. 58 (2): J51–J54. doi:10.3314/mmj.17.005. PMID 28566667.