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

Background: 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. Methods: 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. Results: 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. Conclusions: 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.