Impact of an MRSA Outbreak on Hospital Costs

Background: MRSA is associated with increased healthcare costs for individual colonized and infected patients.  The overall unit and hospital costs attributable to an MRSA outbreak are not as clearly defined. 

Objective: To evaluate the impact of a 13 month MRSA outbreak on total hospital and unit costs.

Methods: Time series analysis was used to compare cost trends on the outbreak unit (a 64 bed internal medicine unit) and a control unit (a 20 bed oncology and HIV unit) over three time periods:  pre-outbreak (Jan 2002 to Aug 2006), outbreak (Sep 2006 to Sep 2007) and post-outbreak (Oct 2007 to Jun 2008).  All patients admitted to the outbreak or control unit were included regardless of their MRSA status.  The total hospital cost per patient was the primary outcome measure and included human resource, overhead, equipment, radiology, laboratory, and pharmacy costs obtained through a centralized accounting system.

Results: The patient population on both units was stable in all study periods in terms of age, gender and case-mix group with a mean age of 63.5 yrs and 54.7 yrs on the outbreak and control units, respectively.  The incidence of new MRSA colonization or infection on the control unit ranged from 1.3 per 1000 patient-days (pre-outbreak) to 2.7 per 1000 patient days (outbreak) to 0 per 1000 patient days (post-outbreak).  Nosocomial MRSA incidence on the outbreak unit rose from 3.5/1000 patient days (pre-outbreak) to 16.6/1000 patient days (outbreak) and then decreased to 3.3/1000 patient days (post-outbreak).  After adjusting for seasonal variation, no significant changes in total hospital cost per patient were seen on the control unit ($11,125 to $11,565 per patient in the pre-outbreak and outbreak period, respectively).  On the outbreak unit, the total hospital cost per patient rose 34.7% during the outbreak (from $9868 to $13,296).  A 13.7% increase in mean hospital length of stay, from 7.3 to 8.3 days, partially accounts for these excess costs.  These data suggest that the outbreak cost the hospital nearly $10 million over the course of the outbreak.

Conclusions: A 13 month MRSA outbreak on our inpatient medical unit resulted in substantial increases in the overall cost per patient on the outbreak unit.  These changes were temporally associated with the outbreak and were not seen on a control unit, suggesting the increases in cost were related to the outbreak.  The overall excess cost accrued to the hospital was significantly higher than what would be predicted from the literature.