Los Límites de los Ensayos Clínicos o la Reunificación de la Epidemiología Translated title: Clinical trials' limits or reunifying epidemiology

New England Journal of Medicine, 342(25), 1887-1892

A large portion of current epidemiologic research is based on methodologic individualism: the notion that the distribution of health and disease in populations can be explained exclusively in terms of the characteristics of individuals. The present paper discusses the need to include group- or macro-level variables in epidemiologic studies, thus incorporating multiple levels of determination in the study of health outcomes. These types of analyses, which have been called contextual or multi-level analyses, challenge epidemiologists to develop theoretical models of disease causation that extend across levels and explain how group-level and individual-level variables interact in shaping health and disease. They also raise a series of methodological issues, including the need to select the appropriate contextual unit and contextual variables, to correctly specify the individual-level model, and, in some cases, to account for residual correlation between individuals within contexts. Despite its complexities, multilevel analysis holds potential for reemphasizing the role of macro-level variables in shaping health and disease in populations. Show more

The double-blind randomized controlled trial (RCT) is accepted by medicine as objective scientific methodology that, when ideally performed, produces knowledge untainted by bias. The validity of the RCT rests not just on theoretical arguments, but also on the discrepancy between the RCT and less rigorous evidence (the difference is sometimes considered an objective measure of bias). A brief overview of historical and recent developments in "the discrepancy argument" is presented. The article then examines the possibility that some of this "deviation from truth" may be the result of artifacts introduced by the masked RCT itself. Can an "unbiased" method produce bias? Among the experiments examined are those that augment the methodological stringency of a normal RCT in order to render the experiment less susceptible to subversion by the mind. This methodology, a hypothetical "platinum" standard, can be used to judge the "gold" standard. The concealment in a placebo-controlled RCT seems capable of generating a "masking bias." Other potential biases, such as "investigator self-selection," "preference," and "consent" are also briefly discussed. Such potential distortions indicate that the double-blind RCT may not be objective in the realist sense, but rather is objective in a "softer" disciplinary sense. Some "facts" may not exist independent of the apparatus of their production. Show more