The costs of nosocomial infections

Background: Although nosocomial infections (NIs) are widely regarded as expensive complications of healthcare delivery, their costs have not been rigorously quantified in large-scale studies. Additionally, problems that can bias cost estimates have often gone unaddressed. For example, are NIs more likely to cause significant extra length of stay (LOS) and costs, or are they more likely to be relatively inexpensive and inevitable consequences of long and expensive hospitalizations? This study is the largest of its kind to provide a rigorous analysis of the costs of NIs. Objective: To precisely bound the attributable costs of a NI using large-scale data and to determine the effects of endogencity between NIs and LOS on cost estimates. Design, Setting and Patients: Discharge diagnoses, cost, LOS, and NI data were collected for 1,355,347 admissions from March 30, 2001 to January 31, 2006 in 55 hospitals. Main Outcome Measures: The cost effects of NIs (in 2007 $) were estimated using multivariable regression models. Restricted models were applied to determine how cost estimates are confounded by disease severity and LOS. Results: NIs are associated with $12,197 (95% CI, $4862-$19,533, P < 0.001) in incremental cost. A lower bound estimate of infection cost, controlling for LOS, is $4644 (95% CI, $1266-$7391). Conclusions: NIs are associated with substantial increases in the costs of inpatient care, even when estimates are corrected for potential endogenous confounding.