A PERSPECTIVE OF EVIDENCE-BASED MEDICINE

S. Kadiri

Department of Medicine, University College Hospital, Ibadan.

Evidence based-medicine (EBM), as currently known, emerged from team work at McMaster University in Canada in the eighties, and the concept is credited to Dr. David Sackett and Dr. Gordon Guyatt. According to one of the originators of the idea, evidence-based medicine is the conscientious, explicit and judicious usev of current best evidence in making decisions about the care of individual patients.¹ Another definition states that evidence-based medicine is the integration of best research evidence with clinical expertise and patient values. Much of that, of course, was founded on the original ideas enunciated by Archie Cochrane, a Scottish epidemiologist after whom the Cochrane Collaboration and Library, a veritable repository of clinical evidence, was named. A parallel can be drawn here with the other situation where another Scot, Dr. Ronald Harden had pioneered one of the major advancements in examination procedure, the Objective Structured Clinical Examination (OSCE), his invention having also burgeoned in parts of North America before receiving world-wide recognition. These definitions of EBM not only reveal its very inclusive nature, but indeed emphasise the aspect of individuality. In that regard, EBM is now standard practice in many countries and institutions, and firmly established in curricula, guidelines and operating procedures. There is evidence though that physicians’ perceptions, knowledge and practice of EBM differ widely.²

An empirical approach to clinical problems is often adopted especially in the face of inadequate resources but, even in that event, the chance of a proper utilization of evidence offers itself. For decades the belief was held that, in order to prevent cardiovascular disease, people above a certain age, variously held to be anywhere from 40 to 50 years, should take a low dose of aspirin daily. However, evidence accumulating over time showed no reduction in first-time cardiovascular events, but rather an increase in bleeding episodes, with some fatality. That did not lead to a discontinuation of the practice, but rather a recommendation that the expected benefits of aspirin use be weighed against the risks. Thus the practice of consumption of daily aspirin continues in those who have had an event and in those with high risk of one.³ New ways of thinking have emerged. It is perhaps no longer totally acceptable to hold a view that the sophisticated mechanisms underpinning a particular therapy ensure its ultimate superiority over others in a clinical setting; it has to be proved.

Although not as frequently mentioned, the concept of evidence applies in other areas such as investigations, teaching methods, all very familiar in medicine, and also in the realms of human behavior and mechanical activities. By and large, evidence addresses, or answers, the question: what is the best possible answer? The presence of evidence has to be seen as an occurrence whose veracity is not dependent on the absence of evidence for some other consideration. Barring direct comparisons of medicines A and B, the finding that medicine A reduces mortality in a certain condition does not detract from the qualities of medicine B, also used in the treatment of that condition. The absence of evidence for the effectiveness of a therapy does not necessarily imply the ineffectiveness of that therapy, but simply states that it has not been ascertained, quite different from ‘evidence shows that it is ineffective.’ The application of evidence ensures that a practitioner remains on a justified, ‘legal’ course, but does not preclude the occurrence of a similar clinical outcome from another line of management, albeit not evidence tested. However, given the contextual nature of evidence, it might change with time or place, hence the need for evaluation of evidence after application.