Structured Expert Elicitation in the Medical Field: A Case Study on Xenotropic Murine Leukemia Virus-Related Virus (XMRV)
Susie ElSaadany
Center for Communicable Diseases and Infection Control, Public Health Agency of Canada, Ottawa, ON, Canada

Issue: The timely attention to risks associated with Xenotropic Murine Leukemia virus-Related Virus (XMRV), a potential blood borne pathogen, may not be achievable using evidence-based research or a traditional Expert Panel process. This process can be expedited by using a Structured Expert Elicitation Methodology, which adds a rational and empirical element to a generally subjective practice.

Emerging blood borne pathogens remains a concern particularly for biological products which cannot undergo rigorous viral reduction and inactivation. Recently XMRV, a human retrovirus, has gained notoriety as a potential emerging blood borne pathogen. Although a causal relationship of XMRV with disease has not yet been established, there is concern regarding the potential transmission of this virus via blood transfusion and via cell, tissue and organ transplantation.

Methodology: Expert Elicitation is a structured and transparent way to address uncertainties. It refers to a structured approach of consulting experts on a subject where there is insufficient knowledge. This risk assessment tool was used to estimate the uncertainty surrounding the emerging threat posed by XMRV and to estimate the magnitude of risk in relation to blood, cells, tissues and organs. The elicitations were conducted using a structured questionnaire and analysed with the Cooke Classical Model and the EXCALIBUR software package. A pool of experts answers calibration questions. The expert responses are scored mathematically. Experts are then elicited individually on target questions. A comparison of different weighting schemes (equal and performance weights) is made. A paired comparison analysis approach was also implemented for certain subsidiary issues.

Results: The elicitation produced quantitative indications of the collective uncertainty judgements of the expert group in relation to thirty-six key factors that might influence XMRV-related disease risks in human beings from blood products. The paired comparison analysis procedure provided an objective assessment of the experts' views on ranking relative risks involved in twelve different aspects of XMRV transmission, such as different blood products, cell transplants, tissue transplants, and surgical procedures.

Conclusions: Elicitation with mathematical formalism can provide estimates with uncertainty ranges for XMRV future modeling until research provides evidence based data.

The results will support policy-decision making related to emerging XMRV risk issues where uncertainty is high.


Cooke, R.M. 1991. Experts in Uncertainty - Opinion and Subjective Probability in Science. Environmental Ethics and Science Policy Series. Oxford University. Press, ISBN 0195064658. pp. 321.

Cooke, R.M. and Goossens, L.H.J. 2008. TU Delft expert judgment data base. Reliability Engineering & System Safety. 93: 657-674.

Keywords: Expert Elicitation; Mathematical for combined expert opinion; Probabilistic inversion; Circular triads

Biography: Chief of the Statistics and Risk Assessment, Blood Safety Surveillance and Health Care Acquired Infections Division, of the Centre for Infectious Disease Prevention and Control in the Population and Public Health Agency of Canada. Adjunct Professor, Department of Pathology and Laboratory Medicine, Faculty of Medicine.

She is a biomathematician/biostatistician, specializing in risk analysis/rapid response risk assessment, utilizing quantitative and probabilistic modelling approaches of rare and emerging infectious diseases.

Her contribution includes risk assessment for rare and emerging diseases involving significant amounts of scientific uncertainty. Additionally, her modelling exercises have helped in forming and framing policy implementation and regulatory measures for Health Canada in relation to blood safety, health care providers and infection control. Her major research focuses on the following: Viral Hepatitis, Creutzfeldt-Jakob Disease, new variant Creutzfeldt-Jakob Disease, Transmissible Spongiform Encephalopathy, Bovine Spongiform Encephalopathy, Severe Acute Respiratory Syndrome, West Nile Virus, Pandemic Flu, and Chronic non-Infectious Diseases.