Evidence of Biological Mechanisms and Health Predictions: An Insight into Clinical Reasoning

Traditionally, the understanding of biological mechanisms has played a central role in clinical reasoning. With the rise of the evidence-based paradigm, however, this role has come under scrutiny. On the one hand, clinical guidelines now place less emphasis on the evidence of pathophysiological mechanisms, a shift motivated by the unreliability of our understanding of complex biological mechanisms. On the other hand, some scholars defend evidence of mechanisms as crucial for clinical practice. This article assesses the relevance of evidence of biological mechanisms in two types of clinical predictions: predictions about the efficacy and about the safety of a certain intervention for a particular patient. For each type of prediction, the article analyzes the two roles that evidence of mechanisms might have-confirming and disconfirming-depending on whether the evidence supports that certain epidemiological results apply to the single patient. The analysis shows that the "unreliability because of incompleteness" argument against the emphasis on mechanistic clinical thinking only applies to some of the considered cases. The article concludes by offering a model for a more granular view of the role that evidence of mechanisms should play in clinical practice.