Greater Hospital-Complexity and Case-Volume are Associated with Lower Mortality among Patients with Staphylococcus aureus Bacteremia
Background: Prior studies have examined hospital-level variation in outcomes for patients hospitalized with common non-infectious conditions, such as myocardial infarction and heart failure. However, little is known about hospital-level variation in outcomes for serious infections. We used a nationwide microbiology database in Veterans Affairs (VA) Healthcare System to quantify hospital-level variation in Staphylococcus aureus bacteremia (SAB) outcomes, and to explore associations between outcomes and hospital characteristics.
Methods: This was a retrospective cohort study of patients admitted to VA hospitals with first episode of community-onset SAB (positive culture within 48 hours of admission) between 2003 and 2010. Patient characteristics and all-cause 30-day mortality were obtained from VA databases; hospital characteristics were from VA organizational surveys. We used hierarchical logistic regression to calculate risk-adjusted mortality for each hospital, and to evaluate associations between hospital characteristics and patient-level mortality. Patient-level variables included demographics, comorbidities, year of admission, prior hospitalization, methicillin susceptibility of culture isolate, vital signs, and laboratory tests at the time of admission.
Results: Analyses included 27,380 patients in 122 hospitals. Overall crude mortality was 16.0%, and ranged from 6.8% to 30.2% across hospitals. After adjusting for patient characteristics (i.e. "case-mix") hospital-level mortality ranged from 8.8% to 22.4% (Figure). Mortality was lower among patients admitted to hospitals with larger case volumes [>60/year vs. <15/year: OR 0.70 (0.56-0.86)], higher ICU complexity [complex ICU vs. no ICU: OR 0.47 (0.24-0.93)], and academic affiliations [OR: 0.70 (0.53-0.94)]. Hospital characteristics were more strongly associated with patient mortality than was methicillin susceptibility of the isolate (MRSA vs. MSSA: OR 1.13 (1.05-1.21).
Conclusion: Greater hospital-complexity, case-volume, and academic affiliation are associated with lower mortality among patients with SAB. Further study is needed to identify modifiable hospital characteristics and to direct quality-improvement efforts.
K. Richardson, None
E. Perencevich, None
M. Vaughand-Sarrazin, None
M. Ohl, None