Role of Comorbidity in Mortality Related to Staphylococcus aureus Bacteremia: A Prospective Study Using the Charlson Weighted Index of Comorbidity

Abstract

AbstractObjective:To demonstrate the effectiveness of the Charlson weighted index of comorbidity (WIC) for controlling comorbidity in prospective studies focusing on mortality in patients with Staphylococcus aureus bacteremia (SAB).Design:Cohort study.Setting:Two tertiary-care, university-affiliated hospitals in France.Patients:One hundred sixty-six inpatients 18 years or older consecutively diagnosed with SAB from May 15, 2001, to May 15, 2002.Methods:Patients were prospectively assessed and cases were followed by the infectious diseases consult service at least 3 months after effective antibiotic therapy completion. The Charlson WIC was computed and dichotomized into scores of fewer than 3 points and 3 or more points. Bacteremia source, acute complication due to SAB acquisition in the ICU, and inappropriate empiric antibiotic therapy were recorded. The endpoint was death due to SAB and overall mortality.Results:In univariate analysis, the Charlson WIC was able to predict overall mortality and S. aureus-related death. The following variables were found to be independently predictive of mortality due to SAB using the Cox model: an acute complication due to S. aureus (OR, 8.9; CI95, 4 to 19.7; P < .001), a Charlson WIC score of 3 or more (OR, 3; CI95, 1.3 to 5.5; P = .006), and age (OR, 1.04; CI95, 1.009 to 1.07; P < .01).Conclusions:Comorbidity contributes to death in patients with SAB. The Charlson WIC is a good predictor of mortality in this population and may be a useful instrument to control comorbidity in studies aiming to investigate risk factors for death due to bacteremia.