For diagnosing tinea, which test is most definitive?

For diagnosing tinea, which test is most definitive?

• A. Potassium hydroxide (KOH) preparation
• B. Culture of lesion scraping
• C. Wood lamp examination
• D. Skin biopsy

Answer: (B)

Culturing the lesion scrapings is the most definitive way to diagnose tinea. This approach grows the actual dermatophyte in the lab, allowing you to confirm infection and identify the specific organism, which provides a definitive diagnosis and can guide treatment. A potassium hydroxide prep is useful for quickly checking for fungal elements, but it can miss infections (false negatives) and it doesn’t identify the organism, so it isn’t definitive. Wood lamp examination only helps in certain species that fluoresce and isn’t reliable for many dermatophytes. A skin biopsy can detect fungal elements and rule out other conditions, but it’s invasive and not typically required for straightforward tinea diagnosis.

Culturing the lesion scrapings is the most definitive way to diagnose tinea. This approach grows the actual dermatophyte in the lab, allowing you to confirm infection and identify the specific organism, which provides a definitive diagnosis and can guide treatment.

A potassium hydroxide prep is useful for quickly checking for fungal elements, but it can miss infections (false negatives) and it doesn’t identify the organism, so it isn’t definitive. Wood lamp examination only helps in certain species that fluoresce and isn’t reliable for many dermatophytes. A skin biopsy can detect fungal elements and rule out other conditions, but it’s invasive and not typically required for straightforward tinea diagnosis.