The Impact of Hospital-Acquired Bloodstream Infections

Richard P. Wenzel, Michael B. Edmond, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia, USA


Emerging Infectious Diseases. 2001;7(2) 

In This Article

Baseline Data

Population-based surveillance studies of nosocomial infections in U.S. hospitals indicate a 5% attack rate or incidence of 5 infections per 1,000 patient-days[3,4,5]. With the advent of managed care and incentives for outpatient care, hospitals have a concentrated population of seriously ill patients, so rates of nosocomial infections are probably correspondingly higher[6]. For many larger institutions, the nosocomial infection rate may be closer to 10%.

If 35 million patients are admitted each year to the approximately 7,000 acute-care institutions in the United States, the number of nosocomial infections--assuming overall attack rates of 2.5%, 5%, or 10%--would be 875,000, 1.75 million, or 3.5 million, respectively. If 10% of all hospital-acquired infections involve the bloodstream, 87,500, 175,000, or 350,000 patients acquire these life-threatening infections each year.

The overall or crude rate of death does not distinguish the contribution of the patients' underlying diseases from the contribution of bloodstream infections. Recent data from the Surveillance and Control of Pathogens of Epidemiologic Importance [SCOPE] surveillance system of nosocomial bloodstream infections in U.S. hospitals identified a crude mortality rate of 27%[7], with great variation by pathogen (Figure 1).

Figure 1. Variation in mortality rate by organism causing nosocomial bloodstream infection[7]. The leading four organisms and crude mortality rate are illustrated.

The direct contribution of nosocomial infection, after the contribution of the underlying illnesses is accounted for, is the attributable mortality rate[8]. For example, if a crude mortality rate for nosocomial candidemia of 40% is assumed (as in the SCOPE surveillance system[7]) and three-eighths of the deaths are directly due to the underlying diseases (15% of the 40%), the mortality rate attributable to candidemia would be 25% (40%-15%). Thus, candidemia would contribute five-eighths (25% of the 40%) of the crude mortality rate.


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