Assessing the Risk of Microbial Pathogens: Application of a Judgment-Encoding Methodology

This paper reports the results of a risk assessment of the adverse health effects from ingesting foods contaminated with certain microbial pathogens. The risk assessment was performed as part of a larger project to develop a risk-based sampling methodology for imported foods inspected by the U.S. Food and Drug Administration (FDA). The sampling methodology was put into operation in a computer aid to assist FDA import inspectors in choosing samples to test for violative substances. The computer aid was designed to choose samples so as to maximize the benefit from the sampling plan. The expected benefit of sampling food depends on the probability that a violation exists, the probability that it will be detected by testing, and the risk of illness associated with the violation. While most of this information is available from data collected by the FDA, very little information has been published regarding the relationship between violative substances and human illness, particularly for microbial pathogens. To narrow this information gap, we recruited the assistance of several experts in the fields of microbiology and epidemiology to evaluate the uncertainty surrounding the intake-response relationships for several microbial pathogens. The information collected from the expert elicitation process and documented here cannot substitute for the scientific data needed to accurately estimate dose-response relationships and their variances. Our goal was simply to gather approximations of these relationships to use in the sampling aid. Our results differ from traditional dose-response curves in that we quantified the uncertainty associated with each probability judgment.