Assessing the appropriateness of community-based antibiotic prescribing in Alberta, Canada, 2017-2020, using ICD-9-CM codes: a cross-sectional study

Abstract

Background: Antimicrobial resistance is a rising threat to human health, and, with up to 90% of antibiotics prescribed in the community, it is critical to examine Canadian antibiotic stewardship practices in outpatient settings. We carried out a large-scale analysis of appropriateness in community-based prescribing of antibiotics to adults in Alberta, reporting on 3 years of data from physicians practising in the province.

Methods: The study cohort was composed of all adult (age 18-65 yr) Alberta residents who filled at least 1 antibiotic prescription written by a community-based physician between Apr. 1, 2017, and Mar. 6, 2020. We linked diagnosis codes from the clinical modification of the International Classification of Diseases, 9th Revision (ICD-9-CM), as used for billing purposes by the province's fee-for-service community physicians, to drug dispensing records, as maintained in the province's pharmaceutical dispensing database. We included physicians practising in community medicine, general practice, generalist mental health, geriatric medicine and occupational medicine. Following an approach used in previous research, we linked diagnosis codes with antibiotic drug dispensations, classified across a spectrum of appropriateness (always, sometimes never, no diagnosis code).

Results: We identified 3 114 400 antibiotic prescriptions dispensed to 1 351 193 adult patients by 5577 physicians. Of these prescriptions, 253 038 (8.1%) were "always appropriate," 1 168 131 (37.5%) were "potentially appropriate," 1 219 709 (39.2%) were "never appropriate," and 473 522 (15.2%) were not associated with an ICD-9-CM billing code. Among all dispensed antibiotic prescriptions, amoxicillin, azithromycin and clarithromycin were the most commonly prescribed drugs labelled "never appropriate."

Interpretation: We found that nearly 40% of prescriptions dispensed to 1.35 million adult patients in Alberta's community-based settings over a 35-month period were inappropriate. This finding suggests that additional policies and programs to improve stewardship among physicians prescribing antibiotics for adult outpatients in Alberta may be warranted.

Figure 1:

Three-day look-back period for associating antibiotic dispensations with diagnosis codes, and example claims-based categorizations of dispensations.

Figure 2:

Flow chart showing identification of antibiotic prescriptions for analysis. *Random product of the data collection and maintenance routines of the Pharmaceutical Information Network system.