Fungal Tests

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Also known as: KOH prep, Fungal smear, Mycology tests
Formal name: Potassium hydroxide preparation, Fungal culture, Fungal antigen and antibody tests, and Calcofluor white stain

The Test Sample

What is being tested?

Fungi are microorganisms that exist in nature as either yeast or moulds. There are more than 50,000 species of fungi in the environment, but less than 200 species are associated with human disease. Of these, only about 20 to 25 species are common causes of infection.

Fungal infections represent the invasion of tissues by one or more species of fungi and 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, ringworm, yeast infections that cause white patches in the mouth (thrush) or vaginal itching and discharge. According to the Centres for Disease Control and Prevention (CDC), almost 75% of women will have at least one yeast infection in their lifetime.

Less commonly, fungi may spread from their original location to penetrate to deeper tissues or may cause serious lung infections, blood infections (septicaemia), or systemic infections that can affect any organ in the body. 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 that are immunocompromised, such as those with HIV/AIDS, those who have had an organ transplant, and those 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 their 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 more tests may be required. However, in cases of persistent, deep, or systemic infections when a more definitive diagnosis is needed, it may be followed by additional tests such as culture and susceptibility testing, antigen, and/or antibody tests.

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 blood from a vein, sputum from the lungs, and/or the collection of a tissue biopsy. If meningitis is suspected, a sample of cerebrospinal fluid may be 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.