Measuring the costs of nosocomial infections: methods for estimating economic burden on the hospital.

To compete more effectively for resources, it is increasingly important for infection control practitioners to estimate the costs of nosocomial infections and the amount of money their infection control programs save the hospital. Studies on costs should estimate both extra length of stay and extra costs attributable to infectious complications. Cost estimates should either adjust charges by a cost to charge ratio, which is relatively easy, or estimate hospital costs directly by detailed cost-accounting, which is comparatively more difficult. If there is insufficient time to measure costs concurrently in every infected patient, comparative studies can be done by comparing infected and uninfected patients matched on characteristics that control for the preexisting differences between them. Diagnosis-related groups and the number of diagnoses appear to be useful matching variables because they are strongly associated with both nosocomial infection and length of stay. The final results should be expressed as either potential or actual savings to the hospital, depending on whether significant reductions in nosocomial infection rates have been achieved.