Objectives: In Denmark, general practice is responsible for 75% of antibiotic prescribing in the primary care sector. We aimed to identify practice-related factors associated with high prescribers, including prescribers of critically important antibiotics as defined by WHO, after accounting for case mix by practice.

Methods: We performed a nationwide register-based survey of antibiotic prescribing in Danish general practice from 2012 to 2013. The unit of analysis was the individual practice. We used multivariable regression analyses and an assessment of relative importance to identify practice-related factors driving high antibiotic prescribing rates.

Results: We included 98% of general practices in Denmark (n = 1962) and identified a 10% group of high prescribers who accounted for 15% of total antibiotic prescriptions and 18% of critically important antibiotic prescriptions. Once case mix had been accounted for, the following practice-related factors were associated with being a high prescriber: lack of access to diagnostic tests in practice (C-reactive protein and urine culture); high use of diagnostic tests (urine culture and strep A throat test); a low percentage of antibiotic prescriptions issued over the phone compared with all antibiotic prescriptions; and a high number of consultations per 1000 patients. We also found that a low number of consultations per 1000 patients was associated with a reduced likelihood of being a high prescriber of antibiotics.

Conclusions: An apparent underuse or overuse of diagnostic tests in general practice as well as organizational factors were associated with high-prescribing practices. Furthermore, the choice of antibiotic type seemed less rational among high prescribers.