METHODOLOGY OF INTERVENTION TRIALS IN PRE VENTION

Prevention envisions either a reduction in the incidence of a disease through direct action against its causes, or a reduction of the conseq uences of that disease (especially mortality), by action against the p rocess leading to clinical expression of the underlying pathology. As in therapeutic medicine, preventive measures must be thoroughly evalua ted for efficacy and secondary effects before they become standard rec ommendations. Two levels of evaluation cart be identified: evaluation of feasibility, acceptability, involving quality control of the propos ed programme, evaluation of results according to previously defined an d quantified objectives. In order to demonstrate that the risk-benefit ratio of a preventive strategy is favorable, results in the intervent ion group must be compared with those BI the control group, just as is do,le in therapeutic trials. Further more, prevention applies general ly to healthy subject ie those riot needing medical care and for whom, in the majority of cares, there will be no direct benefit. As re cons equence, careful ethical consideration must be given to such programme . In particular, calculating the risk-benefit ratio must take into acc ount the mental and social well being of people whose lives will be '' medicalized'' as a result of arch intervention. Measurement of the con sequences of such preventive actions on the life style and mental heal th of the population subjected to them necessitates the development of specific tools adapted to such situations. Research in methodology in this area is essential. If a population with almost 100% risk for a d isease can be identified (genetic risk for exemple), agressive prevent ive intervention can be limited to only that group. It must be emphazi ded that identification of subects at risk no matter how reliable, is not art end bt itself: It is only justified, on a medical point of vie w, if we can offer these individuals a preventive programme with demon strated benefit. The primacy of collective benefit over individual int erest mandates that preventive intervention be based on voluntary info rmed consent of the target population. An alternative to individual co nsent could be, in some occasion, a ''collective'' consent.