This retrospective cohort study used TriNetX, a web-based tool for population cohort research, to identify adult patients with and without PCN allergy label diagnosed with bacterial pneumonia. Cohorts were matched for baseline demographics and chronic medical conditions. The 30-day risks of hospitalization, acute respiratory failure, intubation, need for intensive level of care, and mortality were compared. Antibiotics used and their possible adverse reactions were explored.

After matching, there were 68,748 patients in each cohort. Patients with bacterial pneumonia with PCN allergy label had higher risks of hospitalization (risk ratio [RR], 1.23; 95% confidence interval [CI], 1.22-1.24), acute respiratory failure (RR, 1.14; 95% CI, 1.12-1.15), intubation (RR, 1.18; 95% CI, 1.13-1.22), intensive level of care (RR, 1.11; 95% CI, 1.08-1.14), and mortality (RR, 1.08; 95% CI, 1.04-1.13) compared with patients without PCN allergy label. Patients with PCN allergy label had decreased use of PCNs and cephalosporins and increased utilization of other antibiotic classes compared with patients without PCN allergy label. PCN allergy label was also associated with increased risk of adverse drug reactions.