Cost-Effectiveness of Adding De-colonization to a Surveillance Strategy of Screen and Isolation for Hospital Acquired MRSA Infections

Background: In 2007, the Veterans Health Administration (VHA) implemented an active MRSA surveillance strategy in which all patients admitted to VHA hospitals are screened for MRSA, with those who screen positive placed in isolation.  De-colonization (with agents such as mupirocin and chlorhexidine) has been proposed as an addition to this strategy.
Objective: To compare the cost-effectiveness of the proposed MRSA surveillance strategy of active surveillance plus de-colonization (AS+D) with the current VHA strategy of active surveillance alone (AS) and the non-VHA strategy of no surveillance (NS).

Methods: A decision-analytic model was developed for a 90-day horizon using a societal perspective.  Model inputs, taken from published literature where available and supplemented with expert opinion when necessary, for the base-case analysis (and ranges) were the following: admission prevalence of MRSA, 7.5% (4.5%-12.8%); risk of MRSA infection in carriers, 12.8% (7.8%-17.8%); risk of MRSA infection in non-carriers, 6.6% (1.6%-11.6%); direct benefit of de-colonization (reduction in MRSA infection risk), 45% (8%-75%); indirect benefit of de-colonization (percentage of direct benefit conferred to patients not de-colonized), 25% (10%-75%); indirect benefit of isolation, 33% (28%-38%); probability of death due to MRSA infection, 10% (1-30%); cost of MRSA infection, $34,369 ($25,776-$42,961); cost of de-colonization, $25.25 ($18.94-$31.56); cost of isolation, $425 ($318.75-$531.25); cost of screening, $25.00 ($18.75-$31.25); sensitivity of screening, 94.6% (90%-98%); specificity of screening, 96.9% (90%-98%).  Effectiveness outcomes were hospital-acquired MRSA infections and deaths avoided. One-way sensitivity analyses and Monte Carlo simulations were performed. 
Results: In the base case analysis, the AS+D strategy dominated (i.e. average cost per patient was lower and infections and deaths avoided were higher than) both the AS strategy and the NS strategy.  In addition, the AS strategy dominated the NS strategy.  One-way sensitivity analyses demonstrated that the threshold level of reduction in MRSA infection risk of de-colonization at which AS+D would no longer dominate AS was 12.5%.  This corresponds to a number needed to treat of 107.  In the probabilistic sensitivity analysis, the AS+D strategy dominated both the AS and the NS strategies and the AS strategy dominated the NS strategy in 100% of 1,000 Monte Carlo simulations.

Conclusions: These preliminary results suggest a strong economic argument for adding an MRSA de-colonization protocol to the current VHA active surveillance strategy. Future research will account for the dynamic nature of resistance to de-colonization agents, explore the dependency between direct and indirect benefits of de-colonization, and separate infections based on type, location, and/or severity.