Assessment of the Value of Repeated Point-Prevalence Surveys for Analyzing the Trend in Nosocomial Infections

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Abstract
Objective: : To assess the value of repeated point-prevalence surveys in measuring the trend in nosocomial infections after adjustment for case mix.Setting: : A 3,500-bed teaching facility composed of 4 acute care hospitals.Methods: : From May 1992 to June 1996, eight point-prevalence surveys of nosocomial infections were performed in the hospitals using a sampling process. The trend of adjusted nosocomial infection rates was studied for the four surveys that collected data on indwelling catheters. Adjusted rates were calculated using a logistic regression model and a direct standardization method.Results: : From 1992 to 1996, a total of 20,238 patients were included in the 8 point-prevalence surveys. The nosocomial infection rate decreased from 8.6% in 1992 to 5% in 1996 (P< .001). The analysis of adjusted nosocomial infection rates included 9,600 patients. Four independent risk factors were identified; length of stay greater than 12 days, hospitalization in an intensive care unit, presence of an indwelling urinary catheter, and history of a surgical procedure. After adjustment for case mix, the nosocomial infection rate still showed a downward trend (from 7.2% in 1993 to 5.1% in 1996;P= .02).Conclusion: : Adjusted prevalence rates of nosocomial infections showed a significant downward trend during the period of this study.