PROBLEMS IN THE EVIDENCE OF EVIDENCE-BASED MEDICINE

The proposed practice of ''evidence-based medicine,'' which calls for careful clinical judgment in evaluating the ''best available evidence, '' should be differentiated from the special collection of data regard ed as suitable evidence. Although the proposed practice does not seem new, the new collection of ''best available'' information has major co nstraints for the care of individual patients. Derived almost exclusiv ely from randomized trials and meta-analyses, the data do not include many types of treatments or patients seen in clinical practice; and th e results show comparative efficacy of treatment for an ''average'' ra ndomized patient, not for pertinent subgroups formed by such cogent cl inical features as severity of symptoms, illness, comorbidity, and oth er clinical nuances. The intention-to-treat analyses do not reflect im portant post-randomization events leading to altered treatment; and th e results seldom provide suitable background data when therapy is give n prophylactically rather than remedially, or when therapeutic advanta ges are equivocal. Randomized trial information is also seldom availab le for issues in etiology, diagnosis, and prognosis, and for clinical decisions that depend on pathophysiologic changes, psychosocial factor s and support, personal preferences of patients, and strategies for gi ving comfort and reassurance. The laudable goal of making clinical dec isions based on evidence can be impaired by the restricted quality and scope of what is collected as ''best available evidence.'' The author itative aura given to the collection, however, may lead to major abuse s that produce inappropriate guidelines or doctrinaire dogmas for clin ical practice. (C) 1997 by Excerpta Medica, Inc.