Are patient decision aids effective? Insight from revisiting the debate between correspondence and coherence theories of judgment

Research endeavors to determine the effectiveness of patient decision aids (PtDAs) have yielded mixed results. The conflicting evaluations are largely due to the different metrics used to assess the validity of judgments made using PtDAs. The different approaches can be characterized by Hammond’s (1996) two frameworks for evaluating judgments: correspondence and coherence. This paper reviews the literature on the effectiveness of PtDAs and recasts this argument as a renewed debate between these two meta-theories of judgment. Evaluation by correspondence criteria involves measuring the impact of patient decision aids on metrics for which there are objective, external, and empirically justifiable values. Evaluation on coherence criteria involves assessing the degree to which decisions follow the logical implications of internal, possibly subjective, value systems/preferences. Coherence can exist absent of correspondence and vice versa. Therefore, many of the seemingly conflicting results regarding the effectiveness of PtDAs can be reconciled by considering that the two meta-theories contribute unique perspectives. We argue that one approach cannot substitute for the other, and researchers should not deny the value of either approach. Furthermore, we suggest that future research evaluating PtDAs include both correspondence and coherence criteria.