Do C. Difficile Standardized Infection Ratios Predict Antibiotic Use in Acute Care Hospitals Reporting to the National Healthcare Safety Network?

BACKGROUND: The Antibiotic Use and Resistance (AUR) module of the Centers for Disease Control and Prevention’s (CDC’s) National Healthcare Safety Network (NHSN) enables hospitals to report data on antibiotics administered to patients in inpatient care locations. . Hospitals also report Laboratory identified Clostridium difficile events to NHSN, and CDC reports these data on behalf of the hospitals to the Centers for Medicare and Medicaid Services (CMS) in accordance with CMS reporting requirements. Antibiotic use has a central role in the pathogenesis of C. difficile infections, and the purpose of this analysis is to assess whether facility-wide C. difficile event standardized infection ratios (SIRs) are associated with overall antibiotic use rates among acute care hospitals.

METHODS: In 2015, 52 hospitals reported both facility-wide inpatient AU and C. difficile data to NHSN. Standardized Antibiotic Administration Ratios (SAARs) (antibiotic days of therapy (DOT)/ predicted antibiotic DOTs)) were calculated for all antibiotics in the AUR protocol for hospital onset C. difficileevent SIR quartiles. Consecutive pairwise antibiotic use rates across CDI SIR quartiles were compared for statistical significance using a binomial exact with mid-p test using SAS 9.3.

RESULTS: Overall SAARs increased across the three lowest CDI SIR quartiles (1^st to 2^nd SAAR Ratio: 1.142 (1.140, 1.145); 2^nd to 3^rd SAAR Ratio: 1.265 (1.262, 1.268); all p-values < 0.0001, Table). SAARs were highest in the third quartile of the SIR and decreased in the fourth CDI SIR quartile.

CONCLUSIONS: Overall SAARs in 52 acute care hospitals show a statistically significant increase as C. difficile event SIRs increase; except in the highest quartile of SIRs, where antibiotic use data were less precise. This presentation provides useful insight into the relationship between overall inpatient antibiotic use and hospital onset C. difficile events in acute care hospitals. More data is needed to determine if this relationship holds across a larger cohort of acute care facilities.