a b s t r a c t An astonishing volume and diversity of evidence is available for many hypotheses in the biomedical and social sciences. Some of this evidence-usually from randomized controlled trials (RCTs)-is amalgamated by meta-analysis. Despite the ongoing debate regarding whether or not RCTs are the 'gold-standard' of evidence, it is usually meta-analysis which is considered the best source of evidence: meta-analysis is thought by many to be the platinum standard of evidence. However, I argue that meta-analysis falls far short of that standard. Different meta-analyses of the same evidence can reach contradictory conclusions. Meta-analysis fails to provide objective grounds for intersubjective assessments of hypotheses because numerous decisions must be made when performing a meta-analysis which allow wide latitude for subjective idiosyncrasies to influence its outcome. I end by suggesting that an older tradition of evidence in medicine-the plurality of reasoning strategies appealed to by the epidemiologist Sir Bradford Hill-is a superior strategy for assessing a large volume and diversity of evidence.

A B S T R A C T Early intervention has been reported to improve outcome in children with autism spectrum disorders (ASDs). Several studies in the field have been randomized controlled trials (RCTs). The aim of this study was to assess ASD outcome in a large naturalistic study. Two hundred and eight children, aged 20-54 months, with a clinical diagnosis of ASD were given intervention and monitored prospectively in a naturalistic fashion over a period of 2 years. The toddlers were considered representative of all but the most severely multiple disabled preschool children with ASD in Stockholm county. They fell into three cognitive subgroups: one with learning disability, one with developmental delay, and one with normal intellectual functioning. Data on intervention type and intensity were gathered prospectively in a systematic fashion. Intervention was classified into intensive applied behaviour analysis (ABA) and non-intensive, targeted interventions, also based on ABA principles. Children were comprehensively assessed by a research team before the onset of intervention, and then, again, 2 years later. Change in Vineland adaptive behaviour scales composite scores from intake (T1) to leaving the study (T2) was set as the primary outcome variable. The research team remained blind to the type and intensity of interventions provided. One hundred and ninety-eight (95%) of the original samples stayed in the study throughout the whole 2-year period and 192 children had a complete Vineland composite score results both at T1 and T2. Vineland composite scores increased over the 2-year period. This increase was accounted for by the subgroup with normal cognitive functioning. There was no significant difference between the intensive and nonintensive groups. Individual variation was considerable, but no child in the study was ''problem-free'' at follow-up. Our data do not support that children with ASD generally benefit more from the most intensive ABA intervention programs than from less intensive interventions or targeted interventions based on ABA. ß

ABSTRACT. Policies impose lotteries of outcomes on individuals, since we never know exactly what the effects of the policy will be. In order to evaluate alternative policies, we therefore need to make some assumptions about individual preferences, even before social welfare functions are applied. Instead of making a priori assumptions about those preferences that are likely to be wrong, there are two broad ways in which experimental methods are used to evaluate policy. One is to use experiments to estimate individual preferences, valuations and beliefs, and use those estimates as priors in the evaluation of policy. The other approach is to undertake deliberate randomization, or exploit accidental or natural randomization, to infer the effects of policy. The strengths and weaknesses of these approaches are reviewed, and their complementarities identified.

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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 randomised 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 randomised interventional studies can be justified. Following the critical literature, and in particular the work of John Worrrall, 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 randomisation. 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. While 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. ‡ This is a preprint of La Caze A. (2009). Evidence Based Medicine must be…. Journal of Medicine and Philosophy, 34:509–527. The final published version is available at

© 2009 Ward; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License

To appear in Topoi, special issue on

bias and the evidence hierarchy of evidence-based medicine 218 ABSTRACT Proponents of evidence-based medicine (EBM) suggest that a hier-archy of evidence is needed to guide medical research and practice. Given a variety of possible evidence hierarchies, however, the particular version offered by EBM needs to be justified.This article argues that two familiar justifications offered for the EBM hier-archy of evidence—that the hierarchy provides special access to causes, and that evi-dence derived from research methods ranked higher on the hierarchy is less biased than evidence ranked lower—both fail, and that this indicates that we are not epistemically justified in using the EBM hierarchy of evidence as a guide to medical research and practice. Following this critique, the article considers the extent to which biases influ-ence medical research and whether meta-analyses might rescue research from the influ-ence of bias.The article concludes with a discussion of the nature and role of biases in medical research and suggests that medical researchers should pay closer attention to

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