Outpatient visits before and after Lyme disease diagnosis in a Maryland employer-based health plan

Abstract

Background: Insurance claims data have been used to inform an understanding of Lyme disease epidemiology and cost of care, however few such studies have incorporated post-treatment symptoms following diagnosis. Using longitudinal data from a private, employer-based health plan in an endemic US state, we compared outpatient care utilization pre- and post-Lyme disease diagnosis. We hypothesized that utilization would be higher in the post-diagnosis period, and that temporal trends would differ by age and gender.

Methods: Members with Lyme disease were required to have both a corresponding ICD-9 code and a fill of an antibiotic indicated for treatment of the infection within 30 days of diagnosis. A 2-year 'pre- diagnosis' period and a 2-year 'post-diagnosis period' were centered around the diagnosis month. Lyme disease-relevant outpatient care visits were defined as specific primary care, specialty care, or urgent care visits. Descriptive statistics examined visits during these pre- and post-diagnosis periods, and the association between these periods and the number of visits was explored using generalized linear mixed effects models adjusting for age, season of the year, and gender.

Results: The rate of outpatient visits increased 26% from the pre to the post-Lyme disease diagnosis periods among our 317-member sample (rate ratio = 1.26 [1.18, 1.36], p < 0.001). Descriptively, care utilization increases appeared to persist across months in the post-diagnosis period. Women's care utilization increased by 36% (1.36 [1.24, 1.50], p < 0.001), a significantly higher increase than the 14% increase found among men (1.14 [1.02, 1.27], p = 0.017). This gender difference was mainly driven by adult members. We found a borderline significant 17% increase in visits for children < 18 years, (1.17 [0.99, 1.38], p = 0.068), and a 31% increase for adults ≥ 18 years (1.31 [1.21, 1.42], p < 0.001).

Conclusions: Although modest at the population level, the statistically significant increases in post-Lyme diagnosis outpatient care we observed were persistent and unevenly distributed across demographic and place of service categories. As Lyme disease cases continue to grow, so will the cumulative prevalence of persistent symptoms after treatment. Therefore, it will be important to confirm these findings and understand their significance for care utilization and cost, particularly against the backdrop of other post-acute infectious syndromes.

Keywords: Claims analysis; Lyme disease; Maryland; Post-treatment Lyme disease; Tick-borne diseases.

Fig. 1

Study population and sample size included in final analyses

Fig. 2

Unadjusted rate and 95% confidence interval of Lyme disease relevant outpatient visits stratified by pre (24 months prior) vs. post (23 months after) Lyme disease diagnosis period

Fig. 3

Unadjusted rate of Lyme disease-relevant outpatient visits in the 24 months before LD diagnosis (-24 to -1), the month of Lyme disease diagnosis (0), and the 23 months after Lyme disease diagnosis (1 to 23). Note that for monthly data, rate of outpatient visits per person-month is equivalent to the average number of visits per person per month

Fig. 4

Density plot of member-level change in the average number of Lyme disease-relevant outpatient care visits per month from the pre- to the post-Lyme disease diagnosis periods