Analytical Framework for Examining the Value of Antibacterial Products. 5.2.2 Additional MRSA Parameters

04/15/2014

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

Parameter Value
Expected  RDT Adoption Rate 6.4%
US Population 313,232,044
Hospital Admissions Eligible for RDT 20,080,917
Number with MRSA Colonization 2,008,092
Baseline Number That will Acquire MRSA in the Hospital 306,319
Baseline Number That will Develop An Infection 102,106
Baseline Mortality 9,425
Baseline Morbidity 92,681
Projected Number That will be Tested with RDT 1,285,179
Projected Number with MRSA Colonization Among those Tested with RDT 128,518
Projected Number That will Acquire MRSA in the Hospital with RDT 7,842
Projected Number That will Develop an Infection with RDT 2,614
Projected Number That will Die due to MRSA Infection with RDT 241
MRSA Cases Due to Non-Adopters 95,572
Number That will Die due to MRSA Infection Among Non-Adopters 8,822
Projected Mortality 9,063
Projected Morbidity 89,122
MRSA Cases Avoided Due to RDT 3,921

 

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