Demographics of the study groups.

The “retrospective” cohort was those subjects who had both positive Lyme disease tests and contemporaneous clinical documentation supporting that diagnosis. The “referral” cohort included individuals who had been referred for a Lyme disease evaluation, and were further categorized into Active, Past, or Negative (Non-Lyme disease) disease groups based on records review. The referral subjects who were negative were used as control subjects for our analyses.