Outcomes

We measured the main primary and secondary outcomes at the prescriber level as 6 separate metrics: initiation, selection and duration of antibiotics, and initiation, selection and duration of opioids. Based on our previous validation study¹¹ and the proportion of estimated outlier prescribers in previous studies,^13–15 we considered physicians ranked in the top quartile of any of these metrics to be high prescribers for that particular metric.

Primary outcomes included initiation of antibiotic therapy and initiation of opioid therapy. Antibiotic initiation was defined as a physician’s antibiotic prescription volume (number of prescriptions) divided by his or her patient visits to determine the antibiotic initiation rate. This rate of prescribing is highly variable, even after patient characteristics are accounted for,¹⁶ and is strongly correlated with estimated unnecessary antibiotic prescribing (Pearson’s r = 0.93).¹⁷ Opioid initiation was estimated as the volume of opioid prescriptions initiated by a prescriber. We calculated it by dividing the number of patients with 1 or more opioid prescriptions written by a given physician by the number of patients seen by that physician during the study period.

Secondary outcomes included antibiotic selection and duration of treatment, and opioid selection and duration of treatment. We defined antibiotic selection as the proportion of all antibiotics prescribed that were broad-spectrum; broad-spectrum antibiotic classes included penicillin with β-lactamase inhibitor, fluoroquinolones, macrolides, second-and third-generation cephalosporins, and clindamycin. This definition is based on previous studies of broad-spectrum prescribing and identified risk of community-acquired Clostridium difficile infection.^18,19

We defined opioid selection as the proportion of a physician’s patients prescribed an opioid who received a prescription for 1 or more high-dose opioids, defined as any prescription with a dispensed daily dosage greater than 90 morphine milligram equivalents. The 2017 Canadian Guideline for Opioids for Chronic Non-Cancer Pain²⁰ and the CDC [Centers for Disease Control and Prevention] Guideline for Prescribing Opioids for Chronic Pain — United States, 2016²¹ recommend avoiding increasing dosages beyond 90 morphine milligram equivalents or carefully justifying any decisions to titrate to this dose.

We defined duration of antibiotic treatment as the proportion of all antibiotic prescriptions that were prescribed for a duration of longer than 8 days. We selected this threshold because most uncomplicated infections managed in primary care settings require a duration of antibiotic therapy of 7 days or less.²² We defined duration of opioid treatment as the proportion of a physician’s patients prescribed an opioid who had 1 or more opioid prescriptions with a dispensed duration longer than 28 days. The CDC guideline recommends limiting initial opioid treatment for acute pain to 7 days.²¹ The probability of continuing on a long-term (≥ 1 yr) opioid increases substantially when the first prescription supply exceeds 10 or 30 days.²³ We used a conservative estimate of 28 days to identify prescribers who select longer courses of opioid therapy.