Use of expert opinion for animal disease decisions: An example of foot-and-mouth disease status designation

When data representing a preferred measurement of risk cannot be obtained, as is often the case for global animal diseases, decisions that affect millions of people and their animals are typically made based on expert opinion. Expert opinion can be and has been used to address the critical lack of data existing for prevalence and incidence of many global diseases, including foot-and-mouth disease (FMD). However, when a conclusion based on expert opinion applies to a topic as sensitive as FMD, which has tremendous economic, political, and social implications, care should be taken to understand the accuracy of and differences in the opinion data. The differences in experts' opinions and the relative accuracy of an expert opinion elicitation for "diagnosing" country-level FMD presence were examined for the years 1997-2003 using Bayesian methods. A formal survey of eight international FMD experts revealed that individual experts had different opinions as to the probability of finding FMD in a country. However, a weighted average of the experts' responses was relatively accurate (91% sensitivity and 85% specificity) at identifying the FMD status of a country, compared to using a method that employed information available from World Organization for Animal Health (OIE). The most apparent disagreements between individual experts and available information were found for Indonesia, South Korea, and South America, and, in general, the experts seemed to believe that countries in South Asia were more likely to be positive than other countries that reported FMD cases to OIE. This study highlights new methodology that offers a standardized, quantitative, and systematic means by which expert opinion can be used and assessed.