Most patients with suspected tick-borne diseases (TBD) in the Southeastern US did not receive complete testing per established guidelines, indicating a need for improved surveillance strategies to estimate the burden and distribution of causative pathogens of TBD. These findings were published in JAMA Network Open.

Researchers conducted a cross-sectional study at a large health care system affiliated with the University of North Carolina at Chapel Hill between January 2017 and November 2020. They assessed diagnostic testing patterns and TBD incidence among patients who were tested for spotted fever group rickettsiosis (SFGR), ehrlichiosis, and Lyme disease. The primary outcomes were test positivity rates, the number of completed tests, and the incidence of TBD.

A total of 11,367 patients were included in the analysis, representing 20,528 diagnostic test results. The mean patient age was 54 (IQR, 27-66) years, 58.4% were women, and 95% were non-Hispanic White. The majority of patients underwent testing for Lyme disease (58.3%), followed by SFGR (26.5%) and ehrlichiosis (15.1%). Laboratory-confirmed SFGR, ehrlichiosis, and Lyme disease was found among 47 patients (incidence rate, 4.7%, 7.1%, and 0.7%), respectively.


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The researchers found that only 36.5% of the study population were evaluated for more than 1 TBD. Clinicians assessed patients for Lyme disease evenly throughout the year, and testing for SFGR and ehrlichiosis was more commonly performed between March and October. Testing for ehrlichiosis occurred among 55% of the patients who were tested for SFGR, indicating that ehrlichiosis may have been underdiagnosed.

Further analysis showed that 79.3% of SFGR tests and 74.3% of ehrlichiosis tests lacked a paired convalescent sample, making diagnostic interpretation unreliable. The researchers estimated that 187 and 309 misdiagnoses of SFGR and ehrlichiosis may have occurred due to incomplete testing.

Study limitations included the lack of clinical and longitudinal data, and that the study population may not represent all patients who were tested for TBD in the area.

According to the researchers, “these findings underscore the need for better diagnostics and active surveillance programs, particularly for SFGR and ehrlichiosis, to more accurately identify the spatial distribution and risk factors for infection.”

Reference

Brown Marusiak A, Hollingsworth BD, Abernathy H, et al. Patterns testing for tick-borne diseases and implications for surveillance in the southeastern US. JAMA Netw Open. 2022;5(5):e2212334. doi:10.1001/jamanetworkopen.2022.12334