Explanatory and pragmatic attitudes in therapeutic trials

Author(s): Lellouch, J.

Journal/Book: J Chron Dis. 1967; 20: 637-648.

Abstract: The "comparison between two treatments" is a problem which is inadequately specified even in its over-all characteristics. It may imply one of at least two types of problem which are basically different.1. 'The first type corresponds to an explanatory approach, aimed at understanding. It seeks to discover whether a difference exists between two treatments which are specified by strict and usually simple definitions. Their effects are assessed by biologically meaningful criteria, and they are applied to a class of patients which is rather arbitrarily defined, but which is as likely as possible to reveal any difference that may exist. Statistical procedures used in determining the number of subjects and in assessing the results are aimed at reducing the probabilities of errors of the first and second kind.2. The second type corresponds to a pragmatic approach, aimed at decision. It seeks to answer the question-which of the two treatments should we prefer7 The definition of the treatments is flexible and usually complex; it takes account of auxiliary treatments and of the possibility of withdrawals. The criteria by which the effects are assessed take into account the interests of the patients and the costs in the widest sense. The class of patients is predetermined as that to which the results of the trial are to be extrapolated. The statistical procedures are aimed at reducing the probability of errors of the third kind (that of preferring the inferior treatment); the probability of errors of the first kind is 1.0.Most real problems contain both explanatory and pragmatic elements, for ethical reasons. Most trials done hitherto have adopted the explanatory approach without question; the pragmatic approach would often have been more justifiable.It is thus not surprising if these trials, difficult enough in themselves, raise still further difficulties at every stage and finish by satisfying neither doctor nor statistician. These failings have been clearly delineated of recent years. [3-7] The changes in outlook which appear necessary recall the developments in statistical methodology which led from the theory of significance tests to decision theory. The latter is a more inclusive theory, not only mathematically, but also because it makes conclusions rest upon an overall assessment of profits and losses in the widest sense-in exact correspondence with the pragmatic approach.This paper makes no pretention to originality, nor to the provision of solutions; we hope we have clarified certain issues to the extent of encouraging further discussion.

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