Three broad movements are seeking to change the world of medicine. The proponents of 'evidence-based medicine' are mainly concerned with ensuring that strategies of proven clinical effectiveness are adopted. Health economists are mainly concerned to establish that 'cost-effectiveness' and not 'clinical effectiveness' is the criterion used in determining option selection. A variety of patient support and public interest groups, including many health economists, are mainly concerned with ensuring that patient and public preferences drive clinical and policy decisions. This paper argues that decision analysis based medical decision making (DABMDM) constitutes the pre-requisite for the widespread introduction of the main principles embodied in evidence-based medicine, cost-effective medicine and preference-driven medicine; that, in the light of current modes of practice, seeking to promote these principles without a prior or simultaneous move to DABMDM is equivalent to asking the cart to move without the horse; and that in fact DABMDM subsumes and enjoins the valuable aspects of all three. Particular attention is paid to differentiating between DABMDM and EBM, by way of analysis of various expositions of EBM and examination of two recent empirical studies. EBM, as so far expounded, reflects a problem-solving attitude that results in a heavy concentration on RCTs and meta-analyses, rather than a broad decision making focus that concentrates on meeting all the requirements of a good clinical decision. The latter include: ensuring that inferences from RCTs and meta-analyses to individual patients (or patient groups) are made explicitly; paying equally serious attention to evidence on values and costs as to clinical evidence; and accepting the inadequacy of 'taking into account and bearing in mind' as a way of integrating the multiple and distinct elements of a decision.

When a HRQOL measure is needed in health care decision making should it be a generic measure (a GEN), intended to cover the entire domain of health, a condition-specific measure (a CSM) intended to embrace those aspects of health associated with the condition concerned, or both? This paper proposes that it will never be appropriate to use both a CSM and a GEN for the same decision; that a GEN alone will probably be the appropriate measure in the majority of decisions; that a CSM alone will sometimes be appropriate; and that whether it is a GEN alone or a CSM alone that is appropriate depends entirely on the structure of the decision. The argument rests on the distinction between knowledge validity and decision validity. But it has a supplementary basis in rejection of the widespread (but unjustifiable) belief that CSMs are more "sensitive" or "responsive" than GENs and hence can detect "small but important changes" that GENs always or often miss.

In many health decision making situations there is a requirement that the effectiveness of interventions, usually their 'clinical' effectiveness, be established, as well as their cost-effectiveness. Often indeed this is effectively a prior requirement for their cost-effectiveness being investigated. If, however, one accepts the ethical argument for using a threshold incremental cost-effectiveness ratio (ICER) for interventions that are more effective but more costly (i.e. fall in the NE quadrant of the cost-effectiveness plane), one should apply the same decision rule in the SW quadrant, where the intervention is less effective but less costly. This implication is present in most standard treatments of cost-effectiveness analysis, including recent stochastic versions, and had gone relatively unquestioned within the discipline until the recent suggestion that the ICER threshold might be 'kinked'. A kinked threshold would, O'Brien et al. argue, better reflect the asymmetrical individual preferences found in empirical studies of consumer's willingness to pay and willingness to accept and justify different decision rules in the NE and SW quadrants. We reject the validity of such asymmetric preferences in the context of public health care decisions and consider and counter the two main 'ethical' objections that probably underlie the asymmetry in this case--the objection to 'taking away' and the objection to being required to undergo treatment that is less effective than no treatment at all.

The arrival of new analysis‐based decision technologies will necessitate a profound rethinking both of the nature of the patient–doctor relationship and of the way aids and support systems designed to improve decision‐making within that relationship are designed and evaluated. One‐dimensional typologies of the traditional `paternalist/shared/informed' sort do not provide the complexity called for by the heterogeneity of patient's `meta‐preferences' regarding their relationship with a doctor on the one hand and regarding the analytical level of judgement and decision‐making on the other. A multidimensional matrix embodying this distinction is proposed as a framework of the minimal complexity required for the design and evaluation of the full range of decision aids and decision modes. Essentially aids should be conceived of and evaluated cell‐specifically and the search for universally satisfactory decision support systems abandoned. `shared' and `informed' are best interpreted as attributes which may or not be in line with a patient's meta‐preferences. Future research should focus on the higher level goal of better decision‐making, a goal that will need to respect and reflect these meta‐preferences.