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549 The Economic Impact of Antimicrobial Resistance in Patients with Nosocomial Staphylococcus aureus Bacteremia

Saturday, March 20, 2010
Grand Hall (Hyatt Regency Atlanta)
Suzanne T. Phillips, PharmD, MPH, PhD , Evans Army Community Hospital, Colorado Springs, CO
Ronald Polk, PharmD , Virginia Commonwealth University, Richmond, VA
Spencer E. Harpe, PharmD, MPH, PhD , Virginia Commonwealth University, Richmond, VA
Amy Pakyz , Virginia Commonwealth University, Richmond, VA
Michael Edmond, MD, MPH, MPA , Virginia Commonwealth University Medical Center, Richmond, VA
Norman V. Carroll, PhD , Virginia Commonwealth University, Richmond, VA
Elizabeth E. Turf, PhD , Virginia Commonwealth University, Richmond, VA

Background: The proportion of nosocomial Staphylococcus aureus infections caused by methicillin-resistant Staphylococcus aureus (MRSA) has increased from 22% in 1995 to 63% in 2004. Blood stream infections represent the majority (75.5%) of hospital-onset MRSA cases. The economic impact of Staphylococcus aureus bacteremia merits additional investigation.

Objective: To compare the economic consequences of MRSA vs. MSSA bacteremia by (1) comparing the crude difference in total hospital charges and (2) examining the relationships between SAB methicillin susceptibility, LOS, and total hospital charges while adjusting for potential confounders.

Methods: This was a retrospective cohort analysis within Cerner HealthFacts data warehouse. Eligible patients were adult inpatients with SAB discharged between January 1, 2000, and December 31, 2006.  The crude difference in total charges was measured by subtracting the total mean hospital charges for MSSA bacteremia from the MRSA charge.  A generalized linear model using a gamma distribution and log link was used to determine the adjusted hospital charge and post-infection length of stay for the MRSA and MSSA groups.  Path analysis was used to describe the relationships between infection susceptibility status, LOS and total hospital charge. 

Results: During the study period, 930 patients meet all the inclusion and exclusion criteria.  The overall total hospital charge was $111,636 (MRSA = $121,713, MSSA = $97,307.)  The crude difference in mean charge was $24,406.  The multivariable model included predicted a MRSA patient would have an increased total charge of $22,889.  MRSA had a higher total charge but when patients were more severely ill, MRSA charges decreased while MSSA charges increased. The model for LOS predicted a MRSA patient would have an increased post-infection LOS of 1.3 days. The path analysis model indicated the direct and indirect effects of susceptibility status on both post-infection LOS and total charge were relatively small.

Conclusions: This investigation is the first large multi-center investigation to examine the economic impact of MRSA and MSSA bacteremia.  MRSA was associated with a higher total charge and longer post-infection LOS than MSSA patients.  The path analysis model analyzed suggests the actual role of infection susceptibility status on post-infection LOS and total charge was minor.