According to Guleri, et al. (2011), MRSA colonization rate among patients admitted to the hospital ranges from 6 to 11 percent. Further, one third of patients colonized with MRSA tend to go on to develop an infection (Coia, et al., 2006). Another study by Datta & Huang (2008) finds that around 9 percent of patients that develop a MRSA infection die as a result. In a blinded study of MRSA transmission, Fishbain, et al. (2003) find that out of 354 discharged patients who did not have MRSA upon admission, 20 were colonized after being admitted to the hospital due to exposure to MRSA in the hospital setting. This translates to a transmission rate of 1.7 percent (= 20/354).
Based on the information, we use the following estimates in the model:
- MRSA colonization rate: Triangular probability distribution with a lower bound of 6 percent, upper bound of 11 percent, a likely point estimate of 10 percent,
- Percentage of patients colonized with MRSA that develop an infection: Triangular probability distribution with a lower bound of 25 percent, upper bound of 42 percent, a likely point estimate of 33.3 percent,
- Percentage of patients with MRSA infection that die: Triangular probability distribution with a lower bound of 7 percent, upper bound of 11 percent, a likely point estimate of 9.2 percent, and
- Expected MRSA transmission rate: Triangular probability distribution with a lower bound of 1 percent, upper bound of 2.5 percent, a likely point estimate of 1.7 percent.
There are a number of studies that have investigated reductions in MRSA infection cases as a result of institution of a variety of infection control practices, such as hand washing, patient screening, and education. Findings from these studies suggest that MRSA infections can be substantially reduced, 50 to 70 percent, with the implementation of one or more of these strategies (Jernigan & Kallen, 2010). More recently, Guleri, et al. (2011) report a 78 percent reduction in MRSA bacteremias in a UK hospital after implementation of a rapid MRSA screening program. For the model, we use an expected reduction in MRSA transmission of 60 percent due to the implementation of a rapid MRSA screening program that involves testing all patients admitted to the hospital upon visit to the emergency department. For sensitivity analysis, we assume that the parameter follows a triangular probability distribution with a lower and upper bound of 50 and 70 percent, respectively. Based on the above parameters, Table 25 presents the estimated total number of mortality and morbidity cases in the baseline and under RDT adoption in year 2011 as well as other intermediate parameter estimates used in arriving at the projected health outcomes. We use the U.S. Census population projections to estimate the annual number of cases of avoided mortality and morbidity for years 2012 through 2040 used in the model.
Table 25: Estimates of Mortality and Morbidity under the Baseline without RDT and with RDT Adoption, Respectively