When a patient presents with a suspected fungal toenail infection, what is the appropriate initial diagnostic step?

• A. Scrape nail and send for testing
• B. Begin systemic antifungal therapy immediately
• C. Refer to dermatology without testing
• D. Order an X-ray

Answer: (A)

When a suspected fungal toenail infection is in play, the best first move is to obtain a nail specimen for microscopy and culture. Collecting material from the active nail edge and sending it for a KOH preparation lets you look for fungal elements right away, while a fungal culture (and sometimes PAS staining) identifies the organism and confirms that fungi are truly the cause. This confirmation is crucial before starting treatment because many nail changes are non-fungal (trauma, psoriasis, eczema, other dystrophies), and empirical antifungal therapy carries risks and may be ineffective if the etiology isn’t fungal.

Starting systemic antifungals without proof can lead to unnecessary drug exposure, adverse effects, and interactions, especially given the long duration of therapy for toenail infections. An X-ray isn’t needed at this stage unless there’s concern for bone involvement, which is unlikely early on. Referring to dermatology without testing delays definitive diagnosis and management. So, scraping the nail and testing it first is the appropriate initial diagnostic step.