Impact of prior outpatient antibiotic use on mortality for community acquired pneumonia: a retrospective cohort study

BACKGROUND: The purpose of this study was to examine whether prior outpatient antibiotic use is associated with increased 30-day mortality, after adjusting for potential confounders, for those subsequently hospitalized with pneumonia. METHODS: A retrospective cohort study conducted at two tertiary teaching hospitals. Eligible subjects were admitted with a diagnosis of, and had a chest x-ray consistent with, community-acquired pneumonia. Our primary analysis was a multivariable logistic regression with the dependent variable of 30-day mortality. RESULTS: Data was abstracted on 733 subjects at the two hospitals. Mortality was 8.1% at 30-days. At presentation, 55% of subjects were low risk, 33% were moderate risk, and 12% were high risk. In our cohort 17% (n = 128) of subjects received antibiotics within 30-days of presentation. Unadjusted mortality for those who had received prior antibiotics was 7.0% vs. 8.3% for those who had not (p = 0.6). In the multivariable analysis prior use of antibiotics (odds ratio 0.98, 95% confidence interval 0.5–2.1) was not significantly associated with 30-day mortality. CONCLUSION: Receipt of prior outpatient antibiotics is not significantly associated with 30-day mortality for patients hospitalized with pneumonia. Our study supports current efforts to increase the number of patients with pneumonia who are treated as outpatients.