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Fungal Tests

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Also known as: KOH Prep; Fungal Smear; Mycology Tests; Fungal Molecular Tests
Formal name: Potassium Hydroxide Preparation; Fungal Culture; Fungal Antigen and Antibody Tests; Calcofluor White Stain

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The Test Sample

What is being tested?

Fungi are microbes that exist in nature as one-celled yeasts or as branching filamentous molds (also may be spelled "moulds"). Only about 20 to 25 species of fungi are common causes of infection. Fungal tests detect infections and sometimes identify the fungus and help guide treatment. 

Fungal infections range from superficial skin infections to serious deep tissue, blood, lung, or systemic diseases.

  • Superficial fungal infections are very common. They may cause nail infections or itchy, red, scaly skin infections such as those commonly known as athlete's foot, jock itch, and ringworm, or yeast infections that cause white patches in the mouth (thrush) or vaginal itching and discharge. According to the Centers for Disease Control and Prevention (CDC), almost 75% of women will have at least one yeast infection in their lifetime.
  • Lung, blood, and systemic infections: less commonly, fungi cause serious lung infections, blood infections (septicemia), or systemic infections that can affect any organ in the body. Fungal lung infections typically start with the accidental inhalation of microscopic fungal spores. While anyone can get a serious lung or systemic fungal infection, most affected people will only experience mild to moderate flu-like symptoms. However, people who are immunocompromised, such as those with HIV/AIDS, organ transplant recipients, and people with an underlying condition such as diabetes or lung disease are at an increased risk of having a severe fungal infection, a systemic infection, and/or recurrent infections.

Fungal tests are used to detect and identify fungi in order to diagnose infections and help guide treatment. Fungal testing typically includes a microscopic examination of the sample on a slide, sometimes using a preparation or stain to aid in detection of fungal elements. This may be sufficient to determine that the infection is due to a fungus and, with superficial infections, no further testing may be required.

However, in cases of persistent, deep, or systemic infections when a more definitive diagnosis is needed, the microscopic exam may be followed by additional tests, such as culture and susceptibility testing, antigen or antibody tests, or molecular tests that detect fungal genetic material.

How is the sample collected for testing?

The sample collected depends upon the suspected location(s) of the infection. For superficial infections, the sample may include scrapings of the skin, clipped or shaved nail or hair, vaginal secretions collected with a swab, or a urine sample. For deeper tissue, organ, or systemic infections, the sample may involve the collection of urine, blood from a vein, sputum from the lungs, bone marrow, and/or the collection of a tissue biopsy. If meningitis is suspected, a sample of cerebrospinal fluid is collected.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.