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In Canada, C. difficile mortality rate increased fourfold in seven years
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The mortality rate for health care-associated Clostridium difficile was four times higher in a Canadian study conducted in 2004-2005 than it was in a study conducted in 1997. However, the incidence rate of C. difficile infections was similar in both studies.
Researchers from the Canadian Nosocomial Infection Surveillance Program conducted a prospective study of C. difficile infections from November 2004 to April 2005. Emphasis was placed on patient outcomes.
In the recent study, the researchers reviewed data from 1,430 adults who had health care-associated infections. There were 4.6 cases of C. difficile per 1,000 patient admissions. Thirty days after onset of infection, 233 patients died from all causes. There were 31 deaths directly related to C. difficile and 51 deaths indirectly related to C. difficile.
In the 1997 study, the mortality rate attributable to the infection was 1.5%, compared with 5.7% in the recent study (P<0.001). The attributable mortality in the current study was 3.5 times higher in patients aged older than 65 years than it was in patients aged 18 to 64 years, according to the results.
There were 66 cases of C. difficile per 100,000 patient-days in the 1997 study and 65 cases per 100,000 patient-days in the recent study (P<0.001).
Clin Infect Dis. 2009;48:568-576.
This study demonstrates that although overall rates of health care-associated C. difficile have remained stable over the past decade, there have been some notable changes. There is great degree of geographic variation in rates. Whether this is due to antibiotic use, differences in facility characteristics or presence of the hypervirulent outbreak strain is unclear. The attributable mortality was much higher in the current study. This finding is consistent with other reports from 2000 onward (such as the Pittsburgh experience). This is probably due to presence or high incidence of the outbreak strain, particularly since outcomes were notably worse in Quebec/Ontario, where the epidemic strain is known to occur in high levels. Older adults were impacted more frequently and had worse outcomes. This is consistent with the changing epidemiology of C. difficile, particularly since the epidemic strain spread throughout the past decade. Vancomycin seemed to be used for more severe cases of C. difficile, which is consistent with recently published guidelines. The inability of this study to show better outcomes for patients treated with vancomycin as compared to metronidazole likely represents confounding by indication. That is to say, sicker patients receive vancomycin. Those patients in turn have worse outcomes, even if vancomycin works relatively well. Thus, the outcomes of vancomycin vs. metronidazole should not be misconstrued. Bias existing with choice of agent by provider greatly impacts results and outcomes. These results by no means should be interpreted in the same way that results from a controlled trial of vancomycin vs. metronidazole would be interpreted.
– Keith Kaye
Infectious Disease News Editorial Board member