The transferability problem—whether the results of an experiment will transfer to a treatment population—affects not only Randomized Controlled Trials but any type of study. The problem for any given type of study can also, potentially, be addressed to some degree through many different types of study. The transferability problem for a given RCT can be investigated further through another RCT, but the variables to use in the further experiment must be discovered. This suggests we could do better on the epistemological (...) problem of transferability by promoting, in the repeated process of formulating public health guidelines, feedback loops of information from the implementation setting back to researchers who are defining new studies. (shrink)

How can philosophy of science be of more practical use? One thing we can do is provide practicable advice about how to determine when one empirical claim is relevant to the truth of another; i.e., about evidential relevance. This matters especially for evidence-based policy, where advice is thin—and misleading—about how to tell what counts as evidence for policy effectiveness. This paper argues that good efficacy results (as in randomized controlled trials), which are all the rage now, are only a very (...) small part of the story. To tell what facts are relevant for judging policy effectiveness, we need to construct causal scenarios about will happen when the policy is implemented. (shrink)

Proponents of evidence-based medicine (EBM) provide the “hierarchy of evidence” as a criterion for judging the reliability of therapeutic decisions. EBM's hierarchy places randomized interventional studies (and systematic reviews of such studies) higher in the hierarchy than observational studies, unsystematic clinical experience, and basic science. Recent philosophical work has questioned whether EBM's special emphasis on evidence from randomized interventional studies can be justified. Following the critical literature, and in particular the work of John Worrall, I agree that many of the (...) arguments put forward by advocates of EBM do not justify the ambitious claims that are often made on behalf of randomization. However, in contrast to the recent philosophical work, I argue that a justification for EBM's hierarchy of evidence can be provided. The hierarchy should be viewed as a hierarchy of comparative internal validity. Although this justification is defensible, the claims that EBM's hierarchy substantiates when viewed in this way are considerably more circumscribed than some claims found in the EBM literature. (shrink)

Evidence-based medicine (EBM) puts forward a hierarchy of evidence for informing therapeutic decisions. An unambiguous interpretation of how to apply EBM's hierarchy has not been provided in the clinical literature. However, as much as an interpretation is provided proponents suggest a categorical interpretation. The categorical interpretation holds that all the results of randomised trials always trump evidence from lower down the hierarchy when it comes to informing therapeutic decisions. Most of the critical replies to EBM react to this interpretation. While (...) proponents of EBM can avoid some of the problems raised by critics by suitably limited the claims made on behalf of the hierarchy, further problems arise. If EBM is to inform therapeutic decisions then a considerably more restricted, and context dependent interpretation of EBM's hierarchy is needed. (shrink)

The claims of randomized controlled trials to be the gold standard rest on the fact that the ideal RCT is a deductive method: if the assumptions of the test are met, a positive result implies the appropriate causal conclusion. This is a feature that RCTs share with a variety of other methods, which thus have equal claim to being a gold standard. This article describes some of these other deductive methods and also some useful non-deductive methods, including the hypothetico-deductive method. (...) It argues that with all deductive methods, the benefit that the conclusions follow deductively in the ideal case comes with a great cost: narrowness of scope. This is an instance of the familiar trade-off between internal and external validity. RCTs have high internal validity but the formal methodology puts severe constraints on the assumptions a target population must meet to justify exporting a conclusion from the test population to the target. The article reviews one such set of assumptions to show the kind of knowledge required. The overall conclusion is that to draw causal inferences about a target population, which method is best depends case-by-case on what background knowledge we have or can come to obtain. There is no gold standard. (shrink)

Evidence-based approaches to policy-making are growing in popularity. A generally embraced view is that with the appropriate evidence at hand, decision and policy making will be optimal, legitimate and publicly accountable. In practice, however, evidence-based policy making is constrained by a variety of problems of evidence. Some of these problems will be explored in this article, in the context of the debates on evidence from which they originate. It is argued that the source of much disagreement might be a failure (...) to addressing crucial philosophical assumptions that inform, often silently, these debates. Three controversial questions will be raised which appear central to some of the challenges faced by evidence-based policy making: firstly, how do certain types of facts candidate themselves as evidence; secondly, how do we decide what evidence we have, and how much of it; and thirdly, can we combine evidence. In addressing these questions it will be shown how a philosophically informed debate might prove instrumental in clarifying and settling practical difficulties. (shrink)

Nancy is ultimately most concerned about how to determine the relevance of evidence to implementation of evidence-based policy guidelines, in other words, the transferability of study results to a population different from the one that was studied and in which procedures or conditions are not the same as those in the study. And she is concerned about the privileged position Randomized Controlled Trials (RCTs) are given in the ranking schemes for evidence-based policy, because as she sees it RCTs do not (...) address this question while other methods do. RCTs are highly regarded because of their strength in ruling out confounding variables, but they can be weak on the transferability problem because the manipulations necessary for controlled experiment also guarantee that the setting and population are different from the situation and population targeted for application. However, both of these familiar points are simplifications that can be misleading. Some non-RCT type studies (e.g. soft interventions) can also be very good at ruling out confounding variables.1 And, as I will explain, the problems leading to the transferability problem – interacting variables and a difference between study and target populations – are present in any study, not unique to RCTs. In addition. (shrink)

It is surely obvious that medicine, like any other rational activity, must be based on evidence. The interest is in the details: how exactly are the general principles of the logic of evidence to be applied in medicine? Focussing on the development, and current claims of the ‘Evidence-Based Medicine’ movement, this article raises a number of difficulties with the rationales that have been supplied in particular for the ‘evidence hierarchy’ and for the very special role within that hierarchy of randomized (...) controlled trials (and meta-analyses of the results of randomized controlled trials). The point is not at all to question the application of a scientific approach to evidence in medicine, but, on the contrary, to indicate a number of areas where philosophers of science can contribute to a proper implementation of exactly that scientific-evidential approach. (shrink)