Epidemiology of Lyme Disease as Identified Through Electronic Health Records in a Large Midwestern Health System, 2016-2019.

Lyme disease is the most common vector-borne disease in the United States; however, its frequency is not reliably measured through surveillance. Electronic health records (EHR) might capture the frequency and characteristics of Lyme disease cases more accurately. We queried EHR from 1 health system to describe the epidemiology of Lyme disease cases in Wisconsin during 2016-2019. Within a cohort of persons evaluated for Lyme disease, we applied a Lyme disease case definition based on first-line antibiotics within 14 days of a Lyme disease diagnosis code or test order or on the same day as a related keyword in clinical notes. We compared characteristics of cases to those of cases reported through surveillance and reviewed medical charts to assess case definition validity. Among 67 289 possible Lyme disease events in the cohort, 13 494 (20.1%) met our Lyme disease case definition. Cases were more common among males, children 5-9 years, older adults, White non-Hispanic persons, and in the summer months. EHR-based Lyme disease incidence was 4-8 times that reported through surveillance. The EHR definition had moderately high sensitivity (83.4%) and specificity (71.1%) for confirmed and probable Lyme disease. EHR queries show promise to capture the incidence of Lyme disease more completely and provide more robust clinical information than public health surveillance. Demographic and seasonal characteristics of EHR-identified cases were comparable to those identified through surveillance. Further algorithm refinement might improve accuracy of measuring Lyme disease in EHR systems.