What is the primary method for diagnosing impetigo?

• A. Clinical diagnosis; Gram stain & culture if atypical presentation
• B. CT scan
• C. Serology
• D. Skin biopsy

Answer: (C)

Impetigo is diagnosed primarily by its characteristic appearance and clinical course. Typical lesions are superficial vesicles or pustules that rupture and crust over, producing the classic honey-colored crusts, often on the face or exposed areas in children. In most cases, no lab tests are needed—the diagnosis is made from the exam and history, and treatment is guided accordingly.

Gram stain and culture of a crust or vesicle can be helpful when the presentation is atypical, there is treatment failure, concern for MRSA, immunocompromise, or to tailor antibiotic choice based on local resistance patterns. More invasive tests aren’t routinely used because CT scanning, serology, and skin biopsy do not improve diagnostic accuracy for the usual presentation of impetigo. They are reserved for unusual or unclear cases where a different diagnosis is being considered.