Importance: Respiratory pathogen testing has been a common deimplementation focus. The COVID-19 pandemic brought new considerations for respiratory testing; recent trends in testing rates are not well understood.

Objective: To measure trends in respiratory testing among encounters for acute respiratory infections among children and adolescents (aged <18 years) from 2016 to 2023, assess the association of COVID-19 with these trends, and describe associated cost trends.

Design, Setting, and Participants: This retrospective serial cross-sectional study included emergency department (ED) encounters and hospitalizations in US children’s hospitals among children and adolescents with a primary acute infectious respiratory illness diagnosis. Data were ascertained from the Pediatric Health Information System database from January 1, 2016, to December 31, 2023.

Exposure: Respiratory pathogen testing.

Main Outcomes and Measures: The primary outcome was the percentage of encounters with respiratory testing over time. Interrupted time series models were created to assess the association of COVID-19 with testing patterns. The inflation-adjusted standardized unit cost associated with respiratory testing was also examined.

Results: There were 5 090 923 eligible encounters among patients who were children or adolescents (mean [SD] age, 3.36 [4.06] years); 55.0% of the patients were male. Among these encounters, 87.5% were ED only, 77.9% involved children younger than 6 years, and 94.5% involved children without complex chronic conditions. Respiratory testing was performed in 37.2% of all encounters. The interrupted time series models demonstrated increasing prepandemic testing rates in both ED-only encounters (slope, 0.26 [95% CI, 0.21-0.30]; P < .001) and hospitalizations (slope, 0.12 [95% CI, 0.07-0.16]; P < .001). Increases in respiratory testing were seen at the onset of the COVID-19 pandemic in both ED-only encounters (level change, 33.78 [95% CI, 31.77-35.79]; P < .001) and hospitalizations (level change, 30.97 [95% CI, 29.21-32.73]; P < .001), associated initially with COVID-19–only testing. Postpandemic testing rates remained elevated relative to prepandemic levels. The percentage of encounters with respiratory testing increased from 13.6% [95% CI, 13.5%-13.7%] in 2016 to a peak of 62.2% [95% CI, 62.1%-62.3%] in 2022. While COVID-19–only testing decreased after 2020, other targeted testing and large-panel (>5 targets) testing increased. The inflation-adjusted standardized unit cost associated with respiratory testing increased from 34.2 dollars [95% CI, 33.9 dollars-34.6 dollars] per encounter in 2017 to 128.2 dollars [95% CI, 127.7 dollars-128.6 dollars] per encounter in 2022.

Conclusions and Relevance: The findings of this cross-sectional study suggest that respiratory testing rates have increased over time, with large increases at the onset of the COVID-19 pandemic that have persisted. Respiratory testing rates and related costs increased significantly, supporting a need for future deimplementation efforts.