USING AGENT-BASED SIMULATION TO EVALUATE POLICIES FOR CLOSTRIDIUM DIFFICILE INFECTION CONTROL IN A HOSPITAL

Purpose:   Clostridium difficile infection (CDI) affects 500,000 Americans every year, and is responsible for nearly 20,000 deaths annually. Although there are guidelines to control CDI outbreaks in a hospital, there is a strong need to develop rigorous methods to assess the efficacy of these strategies. The purpose of this study is to evaluate the performance of strategies to mitigate disease spread in a hospital. 

Method:   We propose an agent-based simulation to model the effects of infection control strategies to minimize disease transmission rates, CDI-related mortality, and exposure. Agent-based simulation is ideal for studying the interaction between patients that results in disease transmission, because it tracks the behavior of patients, health-care staff, and visitors in the hospital. Patients arrive to the hospital, stay for a random duration, and then leave the system. During their stay, patients may develop CDI or contract CDI from other infected or exposed individuals in the hospital. We analyze the efficacy of various infection control strategies including prophylactic vancomycin treatment, patient isolation, routine bleach disinfection of rooms, and increased hand hygiene measures, and how these strategies affect outcomes such as infection rates and length of stay (LOS). We use data from admissions records from the Wisconsin Hospital Association, which include data from hospitals in the state of Wisconsin from January 2007 to June 2010, covering over two million hospital admissions. 

Result:   Comparing individual strategies to the base case (no strategy), our preliminary results are as follows: Vancomycin treatment leads to a 12.9% reduction in average LOS over all patients, 8.9% less CDI cases, and 5.5% fewer relapse CDI. Infected patient isolation leads to a 14.3% reduction in LOS, 4% fewer CDI cases, and 29.1% fewer relapse CDI. Routine bleach disinfection leads to a 16.6% reduction in LOS, 6.3% fewer CDI cases, and 31% fewer relapse CDI.  Increased hand hygiene leads to a 6.1% reduction in LOS, 5% fewer CDI cases, and 10.9% fewer relapse CDI.  Finally, a comprehensive strategy leads to 59.7% reduction in average LOS, a 25.2% reduction in new CDI, and a 74.1% reduction in relapse CDI.

Conclusion:  Our agent-based model provides a rigorous analytical method for evaluating the efficacy of a customized strategy for combating CDI outbreaks in a hospital, thus leading to shorter LOS, fewer infections, and fewer relapses.