Burden of meticillin-resistant Staphylococcus aureus infections at a Swiss University hospital: Excess length of stay and costs

Background: Meticillin-resistant Staphylococcus aureus (MRSA) infections increase hospital costs primarily by prolonging patient length of stay (LOS). Aim: To estimate the health-economic burden of MRSA infections at a Swiss University hospital using different analytical approaches. Methods: Excess LOS was estimated by: (i) multistate modelling comparing MRSA-infected and MRSA-free patients with MRSA infection as time-dependent exposure; (ii) matching MRSA-infected patients with a cohort of MRSA-uninfected patients. The economic impact was assessed by: (i) comparing cost estimates between MRSA-infected and MRSA-free patients and multiplying excess LOS by bed-day cost; (ii) comparing real costs between MRSA-infected and MRSA-colonized non-infected patients. Findings: The crude mean LOS was 37.3, 33.0 and 8.8 days for MRSA-infected, MRSA-colonized and MRSA-free patients, respectively. Excess LOS attributable to MRSA infection was 11.5 [95% confidence interval (CI): 7.9-15] or 15.3 days according to multistate modelling and matched analysis, respectively. The likelihood of discharge after MRSA infection was significantly reduced (adjusted hazard ratio: 0.69; 95% CI: 0.59-0.81). Average bed-day costs for MRSA-infected patients were 1.49- and 1.26-fold higher than for the general population hospitalized in acute wards and MRSA-colonized patients, respectively. MRSA infection resulted in an average additional cost of about 800 Swiss francs per day. Conclusions: This analysis emphasizes the financial impact of MRSA infections, demonstrates the importance of accounting for time-dependent bias and confirms that multistate modelling is a valid strategy for estimating excess LOS and costs after MRSA infection.