Trends in Commercial Laboratory Testing and Positivity for Bordetella Species in the United States, 2019 Through 2023.

BACKGROUND

Diagnostic methods for detecting infections caused by Bordetella species include culture, polymerase chain reaction (PCR), and serology. As the epidemiology of pertussis continues to evolve in the United States, we aimed to assess recent trends in provider testing practices and positivity for both Bordetella pertussis and Bordetella parapertussis.

METHODS

Using deidentified data from a large US commercial laboratory, we identified Bordetella tests from 2019 through 2023. We described monthly trends in number of tests ordered by test type for culture, PCR (both nonpanel B. pertussis and B. parapertussis tests and those included as part of a respiratory panel), and serology, as well as percent positivity for serology and PCR. We also examined orders and positivity by patient age group and geographic region of the ordering provider.

RESULTS

Among 527 206 tests, we identified 316 428 (60.1%) PCR tests, 204 480 (38.8%) serologic tests, and 5840 (1.1%) cultures. While most PCR tests were ordered as part of a respiratory panel (83.5%), only 215 (0.08%) were positive for B. pertussis. Nonpanel PCR positivity for B. pertussis was substantially higher but variable over the study period, ranging from 3% to 16%. We also observed a notable increase in B. parapertussis positivity on nonpanel PCR tests in the first half of 2023.

CONCLUSIONS

Both PCR and serology remain preferred diagnostic methods for providers. Despite their increasing popularity, B. pertussis positivity remained low for respiratory panels. Data from commercial laboratories can provide crucial insights into pertussis diagnostic trends over time.