In a child with erythema migrans rash due to Lyme disease, is serologic testing required when the rash is present with a history of tick exposure?

• A. Yes, serologic testing is required.
• B. No, serologic testing is never needed.
• C. Only if symptoms occur without the EM rash.
• D. Only in adults.

Answer: (B)

Early Lyme disease with an erythema migrans rash is diagnosed clinically. The EM lesion in the context of tick exposure is enough to start treatment without waiting for blood tests. Antibodies to Borrelia burgdorferi often aren’t yet detectable in the first weeks, so serology at this stage can be negative and would not guide management. The appropriate move is to begin antibiotic therapy based on the clinical picture, rather than rely on serologic testing. Serology may be considered later if symptoms progress or if the diagnosis is uncertain, but at the time EM is present, testing isn’t needed.