Antibiotic prescribing before and after the diagnosis of comorbidity: a cohort study using primary care electronic health records.

BACKGROUND Comorbidities like diabetes or COPD increase patients' susceptibility to infections, but it is unclear how the onset of comorbidity impacts antibiotic use. We aimed to estimate rates of antibiotic use before and after diagnosis of comorbidity in primary care to identify opportunities for antibiotic stewardship. METHODS We analysed UK primary care records from the Clinical Practice Research Datalink (CPRD) database. Adults registered between 2008-2015 without prior comorbidity diagnoses were eligible for inclusion. Monthly adjusted rates of antibiotic prescribing were estimated for patients with new-onset stroke, coronary heart disease, heart failure, peripheral arterial disease, asthma, chronic kidney disease, diabetes or COPD in the 12 months before and after diagnosis, and for controls without comorbidity. RESULTS 106,540 / 1,071,94 (9.9%) eligible patients were diagnosed with comorbidity. Antibiotic prescribing rates increased 1.9-2.3 fold in the 4-9 months preceding diagnosis of asthma, heart failure and COPD, before declining to stable levels within 2 months after diagnosis. A less marked trend was seen for diabetes (Rate ratio 1.55, 95%-CI: 1.48-1.61). Prescribing rates for patients with vascular conditions increased immediately before diagnosis and remained 30-39% higher than baseline afterwards. Rates of prescribing to controls increased by 17-28% in the months just before and after consultation. CONCLUSIONS Antibiotic prescribing increased rapidly before diagnosis of conditions presenting with respiratory symptoms (COPD, heart failure, asthma), and declined afterwards. This suggests onset of respiratory symptoms may be misdiagnosed as infection. Earlier diagnosis of these comorbidities could reduce avoidable antibiotic prescribing.