A nurse is checking a school-age child for pediculosis capitis. Which of the following findings is a definitive indication of this condition?

A. Patchy hair loss can result from excessive scratching, secondary bacterial infection, or other scalp disorders (for example, tinea capitis or alopecia areata). While lice-related scratching can contribute to hair breakage or localized hair loss, hair loss alone is not diagnostic of pediculosis capitis and requires further inspection. B. Intense pruritus is a common symptom of head lice because the host mounts an allergic response to louse saliva. However, itching is nonspecific, many scalp conditions (dandruff, eczema, fungal infections, dermatitis) cause itching, so it cannot definitively establish the diagnosis by itself. C. These findings are characteristic of secondary bacterial infection of the skin, such as impetigo, not of an uncomplicated lice infestation. Although scratching from lice can lead to skin breakdown and secondary infection, crusted, purulent lesions indicate infection that needs separate treatment and are not the hallmark of pediculosis capitis. D. The presence of nits (lice eggs) attached firmly to the hair shaft near the scalp is the definitive sign of pediculosis capitis. Nits do not flake off like dandruff and are the key diagnostic indicator.