Incidence and prevalence of hospital-acquired infections in a cohort of patients admitted to medical departments

INTRODUCTION: Hospital-acquired infections (HAI) are a significant cause of morbidity and mortality. Only point prevalence analyses of HAI have been recorded in Denmark. The aim of this study was to investigate the incidence and prevalence of HAI in patients admitted to departments of internal medicine. MATERIAL AND METHODS: The study involved seven departments and was designed as a cohort study based on reviews of medical records. Except for patients who had previously been admitted within the preceding 30 days, the study included all patients admitted for more than 48 hours during the 45-day study period. HAI was defined according to the criteria established by the Center for Disease Control and Prevention, USA. RESULTS: The incidence of HAI was 1.7 (62/3,568) per 100 days at risk (95% confidence interval (CI) 1.4-2.2), while the total prevalence of HAI was 9.7% (345/3,568) (95% CI 8.7-10.6). Exposure to bladder catheter was associated with an increased risk of urinary tract infection, incidence rate ratio 4.9; (95% CI 1.8-11.5). For the initial 14 days of hospitalization, the incidence of HAI was independent, while the prevalence increased linearly with duration of admittance. CONCLUSION: The incidence of HAI was relatively constant during the initial 14-day-period of hospitalization, suggesting that shortening the period will have no major impact on the incidence of HAI. The prevalence was 9.7%, which is in line with results from prior studies.