Removal · field guidance

Lyme PCR on EM rash biopsy

PCR on a punch biopsy of the leading edge of an EM rash detects Borrelia DNA in 60-80% of cases, mainly used in research and atypical lesions.

Steps

schema.org/HowTo

01
Take a 2-3 mm punch biopsy from the active leading edge of the rash.
02
Submit fresh tissue (not formalin-fixed if possible) for Borrelia PCR.
03
Sensitivity is 60-80% in untreated EM; specificity approaches 100%.
04
Biopsy is rarely needed clinically — EM with epidemiologic exposure is treated empirically.
05
Consider biopsy when the rash is atypical, asymmetric, or otherwise diagnostically unclear.

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