Total Number of Cases that Result in Death
For CUTI, estimates of both mortality and potential long-term morbidity are problematic because they are confounded by the morbidity/mortality of underlying disease and/or injury. Our best source for mortality associated with community-acquired CUTI estimated an overall mortality rate of 13.7 percent, but then concluded that “only 15 [of 43] deaths were attributed directly to bacteremic urinary tract infection according to the criteria used in this study. Of these 15 deaths, 13 occurred among patients on medical services, all but 1 of whom had alcoholic liver disease, malignancy and/or chronic neurologic disease” (Bryan & Reynolds, 1984). For our calculations, we used a mortality rate of 4.8 percent (15 deaths out of 313 cases), although even this adjusted rate might be high.
In the public health report cited above in the calculation of projected healthcare-associated cases, Klevens et al. (2007) estimate that there were 13,088 deaths associated with healthcare-associated urinary tract infections in 2002, which is equivalent to a rate of 4.55 deaths per 100,000 population. In that study, the percentage of patients with a healthcare-associated UTI whose death was determined to be caused by or associated with the UTI from NNIS data was used to estimate the number of deaths. Applied to the 2011 U.S. population, this rate produces 14,259 deaths due to healthcare-associated pneumonia in 2011. Though the 2007 report is not specific with regard to the types of infections that are included (for instance, it may not be strictly limited to complicated UTIs), we used these figures in the absence of better data.
As was done for the other indications, we relied on data from the Compressed Mortality File (from Centers for Disease Control and Prevention, National Center for Health Statistics, available online from CDC WONDER) to approximate a breakdown of deaths by age. Specifically, we utilized a 2008 age distribution of deaths for individuals where the listed cause of death was “Urinary tract infection, site not specified.” This distribution is highly skewed; 92 percent of deaths due to UTIs are among individuals 65 years of age or older. We used this distribution to estimate the number of deaths by age category for 2011. To calculate lost QALYs, we multiplied the number of deaths due to CUTI (redistributed by age group by the breakdowns in the Compressed Mortality File) in each age category by the average years of life remaining for that age group. Life expectancies by age were available from the NVSR. Multiplying the number of deaths by these average life expectancies yields a total of 196,165 QALYs lost due to community-acquired CUTI deaths and 123,748 QALYs lost due to hospital-acquired UTI in 2011 for an overall total of 319,913 QALYs lost.
To calculate VSL-based mortality costs, we multiplied the number of deaths in each age group by the VSL for those age groups. For CUTI, this results in mortality costs of $112 billion and $71 billion for community-acquired and hospital-acquired CUTI, respectively, for an overall total of $183 billion. The average per-patient VSL, weighted by the number of deaths by age, is $4.95 million.