Trends in and Predictors of Carbapenem Consumption across North American Hospitals: Results from a Multicenter Survey by the MAD-ID Research Network

Abstract

We sought to define trends in and predictors of carbapenem consumption across community, teaching, and university-affiliated hospitals in the United States and Canada. We conducted a retrospective multicenter survey of carbapenem and broad-spectrum noncarbapenem beta-lactam consumption between January 2011 and December 2013. Consumption was tabulated as defined daily doses (DDD) or as days of therapy (DOT) per 1,000 patient days (PD). Multivariate mixed-effects models were explored, and final model goodness of fit was assessed by regressions of observed versus predicted values and residual distributions. A total of 20 acute-care hospitals responded. The centers treated adult patients (n = 19/20) and pediatric/neonatal patients (n = 17/20). The majority of the centers were nonprofit (n = 17/20) and not affiliated with medical/teaching institutions (n = 11/20). The median (interquartile range [IQR]) carbapenem consumption rates were 38.8 (17.4 to 95.7) DDD/1,000 PD and 29.7 (19.2 to 40.1) DOT/1,000 PD overall. Carbapenem consumption was well described by a multivariate linear mixed-effects model (fixed effects, R² = 0.792; fixed plus random effects, R² = 0.974). Carbapenem consumption increased by 1.91-fold/quarter from 48.6 DDD/1,000 PD (P = 0.004) and by 0.056-fold/quarter from 45.7 DOT/1,000 PD (P = 0.93) over the study period. Noncarbapenem consumption was independently related to increasing carbapenem consumption (beta = 0.31 for increasing noncarbapenem beta-lactam consumption; P < 0.001). Regular antibiogram publication and promotion of conversion from intravenous (i.v.) to oral (p.o.) administration independently affected carbapenem consumption rates. In the final model, 58.5% of the observed variance in consumption was attributable to between-hospital differences. Rates of carbapenem consumption across 20 North American hospitals differed greatly, and the observed differences were correlated with hospital-specific demographics. Additional studies focusing on the drivers of hospital-specific carbapenem consumption are needed to determine whether these rates are justifiable.

Keywords: antimicrobial stewardship; beta-lactams; consumption; epidemiology; pharmacoeconometrics.

FIG 1

Correlations between carbapenem and noncarbapenem consumption across 20 North American hospitals. Data represent correlations between carbapenem and noncarbapenem consumption with and without outlier removal. (A) Correlation of carbapenem and noncarbapenem DDDs/1,000 PD across all centers and quarters. r = 0.65; R² = 0.427. (B) Correlation between carbapenem and noncarbapenem DOTs/1,000 PD across all centers and quarters. r = 0.94; R² = 0.877. (C) Reanalysis of data presented in panel A with 24 observations from two outlier institutions removed from analysis. r = 0.43; R² = 0.187. (D) Reanalysis of data presented in panel B with 12 observations from a single outlier institution removed from analysis. r = 0.11; R² = 0.012.

FIG 2

Population-level and individual hospital-level observed and model-predicted carbapenem consumption rates. (A) Fixed-effects model, predicted versus observed carbapenem consumption. (B) Fixed- plus random-effects model, predicted versus observed carbapenem consumption.