Variations in Neonatal Antibiotic Use.

OBJECTIVES: We sought to identify whether and how the NICU antibiotic use rate (AUR), clinical correlates, and practice variation changed between 2013 and 2016 and attempted to identify AUR ranges that are consistent with objectively determined bacterial and/or fungal disease burdens.

METHODS: In a retrospective cohort study of >54 000 neonates annually at >130 California NICUs from 2013 to 2016, we computed nonparametric linear correlation and compared AURs among years using a 2-sample test of proportions. We stratified by level of NICU care and participation in externally organized stewardship efforts.

RESULTS: By 2016, the overall AUR declined 21.9% (95% confidence interval [CI] 21.9%-22.0%), reflecting 42 960 fewer antibiotic days. Among NICUs in externally organized antibiotic stewardship efforts, the AUR declined 28.7% (95% CI 28.6%-28.8%) compared with 16.2% (95% CI 16.1%-16.2%) among others. The intermediate NICU AUR range narrowed, but the distribution of values did not shift toward lower values as it did for other levels of care. The 2016 AUR correlated neither with proven infection nor necrotizing enterocolitis. The 2016 regional NICU AUR correlated with surgical volume (ρ = 0.53; = .01), mortality rate (ρ = 0.57; = .004), and average length of stay (ρ = 0.62; = .002) and was driven by 3 NICUs with the highest AUR values (30%-57%).

CONCLUSIONS: Unexplained antibiotic use has declined but continues. Currently measured clinical correlates generally do not help explain AUR values that are above the lowest quartile cutpoint of 14.4%.