Using a randomised controlled trial to test the effectiveness of social norms feedback to reduce antibiotic prescribing without increasing inequities

Abstract

Aims: Antibiotic overprescription is a key driver of antimicrobial resistance, and rates of community dispensing of antibiotics in New Zealand are high compared to other developed countries. We aimed to test whether a social-norm-based intervention successful elsewhere would have an effect on GPs with high prescribing rates of antibiotics. We also aimed to assess the effects on prescribing for Māori and Pacific patients.

Methods: A randomised controlled trial (n=1,214) tested the effects of a letter mailed to high-prescribing GPs that presented their prescribing data in comparison to their peers.

Results: In September-December 2019, after the letters were mailed, the antibiotic prescribing rate in the control arm was 178.8 patients prescribed antibiotics per 1,000 patients prescribed any medicine, and in the intervention arm it was 162.3, a relative difference of 9.2% (p<0.001). GPs in the intervention arm were responsible for an average of 173.5 prescriptions, versus an average of 186.8 prescriptions for GPs in the control arm, a relative difference of 13.3 or 7.1% (p<0.01). Exploratory analyses showed the intervention reduced prescribing to Māori and Pacific patients among historically high prescribing GPs but had no statistically significant impact on low prescribers.

Conclusions: A targeted intervention using social norms reduced prescribing of antibiotics by high-prescribing GPs. Such an approach may be promising to address inequities in access to and use of antibiotics by Māori and Pacific peoples, historically underserved by prescribers, but further investigation is needed.