Table 1.

Patient groups and selection criteria for samples with isolated B. burgdorferi IgM results

Patient group	Allocation criteria
Probable acute LB	• Clinical history/symptoms: EM rash, tick bite and rash or specific neurological symptoms, i.e. facial palsy • Onset < 10 weeks • Follow-up sample consistent with LB
Possible acute LB	• Clinical history/symptoms: tick bite/exposure and flu-like symptoms • Onset < 10 weeks
Not consistent with acute LB	• Non-specific symptoms and/or not thought to be LB by a clinician (via questionnaires) • Symptoms of late LB, i.e. monoarthritis • Onset > 10 weeks
Insufficient clinical details and data	Insufficient or no clinical details