KOH examination to diagnose fungal skin and nail

KOH microscopy is a simple, easy-to-implement technique for diagnosing skin fungus and nail fungus with highly accurate results. After confirming the diagnosis, the patient will be treated according to the appropriate regimen.

Tinea capitis is a skin condition caused by a fungus. The disease often appears in many places on the body, especially those with keratin such as skin, hair, hair, nails, causing discomfort and inconvenience to patients in daily activities.
Some common fungal skin diseases:
Ringworm: Caused by pityrosporum fungus. There are 2 types of viburnum: white and black. The disease causes itching, especially when exposed to the sun or sweat a lot. The risk of disease depends on the hygiene of the skin, the body's resistance, moisture and the pH of the skin; Ringworm: There are symptoms of itching, then a red streak, clearly bordered, bordered and on the edge there are flecks of spots, which can spread to many other areas of the body when the patient scratches. Ringworm is easily spread when sharing household utensils, sleeping in the same bed,...; Interstitial fungi: Caused by fungi epidermophyton, fungi trichophyton, candida albicans. The disease is common in people with occupations that have to soak their feet in water for many hours for a long time such as farmers, sanitation workers, swimmers,...;

Nail fungus: Usually caused by trichophyton fungus, candida albicans fungus. Manifestations of the disease are nail discoloration, protrusion or defect, on the nail surface holes or grooves, increasingly rough, yellow or opaque, may be swollen and festering skin in the corner of the nail; Hair fungus: Caused by the fungus piedra hortai, the disease manifests itself as many black seeds on each hair. If the hair fungus is caused by the fungus trichophyton, there will be lesions on the scalp that are many small round spots with the size of 3-5mm, the scalp has thin scales, itchiness in the head area,... Clinically, depending on Different types of fungi will have different lesions on the skin. For treatment to be successful, patients need to be diagnosed early. Patients suspected of having fungal skin and nail fungus should be tested for tinea versicolor. Commonly used test methods are: Direct microscopy (KOH) or fungal culture on suitable media to identify pathogenic fungi.

Usually, doctors can't accurately diagnose tinea versicolor, nail fungus based on appearance alone. KOH smear is a commonly used method to determine if a person has fungal skin, nail fungus or not.
With this method, the doctor will use a scalpel or another instrument to take a tissue sample. The tissue sample is then smeared with KOH and heated to lyse keratin, the main component of nails and skin. Once these substances have been removed, the doctor can determine the composition of the fungus under the microscope.

When there are patches of skin that are itchy, red, scaly and raised at the edges like blisters; Brittle, brittle, thickened and deformed nails; Appearance of white patches in the mouth; Vaginal itching, discharge.

4.1 Preparation of Tools: Optical microscope, slide, slide, sterilized scalpel, nail clippers, alcohol lamp and alcohol 90°, hair tweezers, 10 - 30% KOH solution; Patient: Listen to the doctor's instructions and explanation of the test procedure. 4.2 Sampling Skin specimen collection: Scrape off the skin at the edge of the lesion; Shave in multiple positions; Shave from the inside of the lesion to the outside of the healthy skin to remove scales at the boundary between the diseased skin and the healthy skin; Place skin flakes on the slide or place in a sterile petri dish; Remove scabs that are not secretory scales; Do not scrape specimens over acute lesions such as acute eczema or superinfection; Take samples from the nail: If the nail lesion is thick at the free edge, use a knife, scissors to scrape and cut the stratum corneum under the nail; If the nail injury separates between the nail and the nail plate, use a sharp knife to scrape off the horny substance under the nail; If inflammation around the nail, scrape off the scab in the groove around the nail; Place the stratum corneum on a sterile slide or petri dish.

4.3 Making slides Place 1-2 drops of fresh reagent on the slide; Cover the lamella; Wait about 15 - 30 minutes or if you want to observe immediately, heat it on the flame of an alcohol lamp; Spread the slides thinly, examine the slide under 10x and 40x objective microscopes; Record the results obtained on the test sheet; Handling instruments and specimens.

5.1 Normal results No fungus was found on the skin, in the nail sample. However, it is possible to repeat the test, taking more samples from different areas of the infected skin or nail to confirm the diagnosis. If the results are normal, your doctor may perform other tests to determine the cause of the skin or nail damage.
5.2 Abnormal results There is fungus in the skin and nail samples for testing.
Gray fungus: Common on the palm, mycelium has septum, bar divider and dark color; Yeast mushroom: Mycelium is coarse, short, round cell cluster has the shape of a toad's egg sac; Dermatophytes: Hyphae are transparent, septa, and stinging spores can be seen; Hair fungus: The filaments and fungal spores are found in the hair shaft (internal) and the mycelium is located around the hair (external).

Factors affecting test results:
Specimen: Before taking the test, the patient needs to stop taking antifungal medication for at least 1-2 weeks. If the drug is not stopped, the fungus temporarily disappears or is recessive, so it is difficult to detect; Ointments that exist on the skin can make it difficult to observe and diagnose tinea versicolor, onychomycosis; The dyes make the skin stained, obscure the structure of the fungus, making it difficult to diagnose; The mycological technician should have a prior orientation on the basis of clinical symptoms of the disease; Pay attention to the hygienic conditions of the equipment and the air at the test site because spores and mycelia often appear in the air, so if you do not pay attention to cleanliness, it is easy to infect and affect the results. test.

In addition to the KOH method of diagnosing skin fungus, nail fungus, doctors can diagnose the disease through fungal culture testing techniques, combined with clinical symptoms of the disease. When the diagnosis is confirmed, the patient will be prescribed an appropriate antifungal drug for active and effective treatment.
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