PURPOSE: Public disclosure of institutional nosocomial infection rates is proposed as a means of improving the quality of medical care. However, institutions use differing diagnostic criteria and do not mandate uniform levels of surveillance. This study assessed the effects of varying diagnostic criteria and intensity of surveillance on ventilator-associated pneumonia (VAP) rates.
METHODS: We prospectively studied all patients receiving mechanical ventilation at our hospital. Each patient was evaluated for VAP using four different criteria: clinical diagnosis by the treating physician; American College of Chest Physicians (ACCP) criteria; Clinical Pulmonary Infection Score (CPIS) >6; and National Nosocomial Infection Survey (NNIS) criteria. VAP incidence rates were calculated using each set of diagnostic criteria. The effect of active VAP screening was assessed by comparing the VAP rate using NNIS criteria prospectively for all patients to the VAP rate reported by the institutional infection control office using the NNIS criteria retrospectively for patients with positive culture data.
RESULTS: 134 patients received mechanical ventilation for >48 hours during the 90-day study period (mean 6.4±8.0 days). VAP rates were 22% using treating physician’s clinical diagnosis, 29% using ACCP criteria, 25% using the CPIS, and 31% using NNIS criteria. The correlation among diagnostic strategies was high only for the ACCP and NNIS criteria (Pearson correlation coefficient 0.95). Correlation coefficients for the remaining strategies ranged from 55% to 67%. Active application of the NNIS criteria to all patients resulted in a significantly higher VAP incidence rate (31%) than if the NNIS criteria were passively used according to institutional infection control policy (2%).
CONCLUSION: Despite increasing support for public disclosure of nosocomial infection rates, the optimal criteria to diagnose VAP are controversial. This is illustrated by the low correlation between the four strategies most commonly used to diagnose VAP. These data highlight how dramatically VAP rates are affected by the choice of diagnostic criteria and the intensity of VAP surveillance.
CLINICAL IMPLICATIONS: Meaningful public disclosure of VAP rates requires standard diagnostic criteria that are applied consistently across institutions.
DISCLOSURE: Lee Morrow, University grant monies Creighton University Health Futures Foundation; Grant monies (from sources other than industry) National Institutes of Health, American College of Chest Physians - Association of Subspecialty Professors; Grant monies (from industry related sources) Pfizer, Hospira, C.R. Bard; Consultant fee, speaker bureau, advisory committee, etc. Pfizer, Boehringer-Ingelheim, Glaxo-SmithKline, Schering-Plough