Which diagnostic test confirms a suspected tinea corporis diagnosis?

Which diagnostic test confirms a suspected tinea corporis diagnosis?

• A. Bacterial culture
• B. KOH with septate hyphae
• C. Gram stain
• D. Wood's lamp blue

Answer: (B)

Diagnosing a suspected tinea corporis relies on directly observing fungal elements in skin scrapings. When you treat a scale sample with potassium hydroxide, the keratin dissolves and fungal structures become visible under a microscope. In dermatophyte infections like tinea corporis, you look for narrow, translucent hyphae with clear internal divisions—septate hyphae—often accompanied by arthroconidia. Seeing these septate hyphae confirms the fungal dermatophyte infection. Wood's lamp can aid only for certain species that fluoresce, and many dermatophytes do not, so it isn’t a reliable confirmatory test. Bacterial culture or Gram stain won’t confirm a fungal infection since they’re designed to detect bacteria rather than fungi.

Diagnosing a suspected tinea corporis relies on directly observing fungal elements in skin scrapings. When you treat a scale sample with potassium hydroxide, the keratin dissolves and fungal structures become visible under a microscope. In dermatophyte infections like tinea corporis, you look for narrow, translucent hyphae with clear internal divisions—septate hyphae—often accompanied by arthroconidia. Seeing these septate hyphae confirms the fungal dermatophyte infection.

Wood's lamp can aid only for certain species that fluoresce, and many dermatophytes do not, so it isn’t a reliable confirmatory test. Bacterial culture or Gram stain won’t confirm a fungal infection since they’re designed to detect bacteria rather than fungi.