KOH Test- Principle, Media, Procedure, Results, Uses


KOH test is a simple and rapid test that can be used to visualize fungal structures in clinical samples. It is based on the principle that potassium hydroxide (KOH) can dissolve the cellular components of human and bacterial cells, but not the fungal cells. This makes the fungal cells stand out against a clear background and allows their identification based on their morphology and arrangement.

KOH test is useful for the presumptive identification of dermatophytes, which are fungi that cause infections of the skin, hair and nails. It can also help in the preliminary diagnosis of other mycoses, which are diseases caused by fungi. KOH test can be performed on various types of clinical specimens, such as skin scrapings, nail clippings, hair, pus, sputum, cerebrospinal fluid (CSF), tissue samples, urine, mucous membrane swabs, bronchial and alveolar washings, etc.

KOH test is easy to perform and does not require complex or expensive equipment or reagents. It can provide results within minutes and help in selecting and initiating appropriate antifungal therapy. However, KOH test has some limitations as well. It cannot provide definitive identification of fungal species or differentiate between viable and non-viable fungal cells. It also requires a skilled person to interpret the results and may not work well with some complex tissue materials that are resistant to KOH digestion.

In this article, we will discuss the objectives, principle, requirements, procedure, results, precautions, applications, advantages and disadvantages of KOH test in detail. We will also compare some modified KOH mount methods that can improve the contrast and staining of fungal cells.