Agreement between units of measure for paediatric antibiotic utilisation surveillance using hospital pharmacy supply data

BACKGROUND: Drug utilisation studies from paediatric hospitals that do not have access to patient level data on medication use are limited by a lack of standardised units of measures that reflect the varying daily dosage requirements among patients. The World Health Organization’s defined daily dose is frequently used in adult hospitals for benchmarking and longitudinal analysis but is not endorsed for use in paediatric populations. OBJECTIVE: Explore agreement between standard adult-based defined daily doses (DDD) and paediatric estimates of daily injectable antibiotic use in a Paediatric Intensive Care Unit that does not have access to individual patient-level data. METHODS: Hospital pharmacy antibiotic use reports and age-specific occupied bed-day data from 1 January 2010 to 31 May 2016 were extracted. Paediatric reference dosages and frequencies for antibiotics were defined and applied to three paediatric units of measure. Measures were applied to extracted data, agreement between antibiotic use measured in the adult DDD and each of the paediatric measures was assessed visually via Bland-Altman plots and linear regression for each antibiotic. RESULTS: Thirty one different antibiotics were used throughout the study period. Despite varying daily dosages in grams, the daily use of vials was unchanged from birth to 18 years for thirteen antibiotics. Agreement between DDD and vial-based measures was closer than the total recommended daily dose that did not account for wastage during preparation and administration. Vial-based measures were unaffected by vial size changes due to drug shortage. CONCLUSIONS: Agreement between the DDD and vial-based measures of use supports the use of DDD for select antibiotics that may be targeted by antimicrobial stewardship programs. Vial based measures should be further explored in hospitals with single vial policies; detailed understanding of hospital practice is needed before inter-hospital comparisons are made.