Interpreting risk as evidence of causality: lessons learned from a legal case to determine medical malpractice

• Published in: Journal of evaluation in clinical practice Vol. 22; no. 4; pp. 515 - 521
• Main Authors: Mercuri, Mathew, Baigrie, Brian S
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.08.2016; Wiley Subscription Services, Inc
• Subjects: Adrenal Cortex Hormones - adverse effects; Bayesian; Causality; Cerebral Palsy - chemically induced; Epidemiologic Methods; evidence; frequentist; Humans; Malpractice - legislation & jurisprudence; Medical malpractice; Ontario; Probability; Risk; Severity of Illness Index; Canada; risk; frequentist; evidence; Bayesian; causality
• ISSN: 1356-1294; 1365-2753
• DOI: 10.1111/jep.12580

Translating risk estimates derived from epidemiologic study into evidence of causality for a particular patient is problematic. The difficulty of this process is not unique to the medical context; rather, courts are also challenged with the task of using risk estimates to infer evidence of cause in particular cases. Thus, an examination of how this is done in a legal context might provide insight into when and how it is appropriate to use risk information as evidence of cause in a medical context. A careful study of the case of Goodman v. Viljoen, a medical malpractice suit litigated in the Ontario Superior Court of Justice in 2011, reveals different approaches to how risk information is used as or might be considered a substitute for evidence of causation, and the pitfalls associated with these approaches. Achieving statistical thresholds, specifically minimizing the probability of falsely rejecting the null hypothesis, and exceeding a relative risk of 2, plays a significant role in establishing causality of the particular in the legal setting. However, providing a reasonable explanation or establishing “biological plausibility” of the causal association also seems important, and (to some) may even take precedent over statistical thresholds for a given context.