A Decade of Prevalence Surveys in a Tertiary-Care Center: Trends in Nosocomial Infection Rates, Device Utilization, and Patient Acuity

Abstract

OBJECTIVE: To evaluate the usefulness of repeated prevalence surveys to determine trends in the rates of nosocomial infections and to detect changes in risk factors (e.g., use of invasive devices) associated with nosocomial infections. PATIENTS AND METHODS: Ten annual prevalence surveys were conducted by trained infection control practitioners between 1985 and 1995 for acute-care patients on the medical, surgical, pediatric, and obstetric-gynecologic services at a 900-bed, tertiary-care, teaching hospital with 750 acute-care beds. The same methods of chart review and concurrent reporting from nursing, the microbiology and clinical laboratory, and the pharmacy were used each year to collect data on the prevalence of nosocomial infections, invasive-device utilization, and abnormal laboratory indicators. Although data were collected on a single day, a period-prevalence study approach was used, because charts were reviewed for any infection data occurring within the 7 days prior to the survey. RESULTS: The hospital census for acute care patients, as measured by the prevalence surveys, declined sharply over the 10 years, from 673 to 575 patients (P = .02). However, the medical service census increased from 150 to 188 patients (P = .01). During the same period, there was a significant decrease in the mean length of stay, from 7.3 to 6.0 days (P = .01), and a concomitant increase in the mean diagnosis related-group case-mix index, from 1.03 to 1.24 (P = .001). Overall, nosocomial infection rates remained unchanged over the study period (mean of 9.85 infections per 100 patients), but rates of nosocomial bloodstream infection increased from 0.0% in 1985 to 2.3% in 1995 (P = .05). Nosocomial infection rates were significantly higher on the medical and surgical services than on other services (P