Evidenced-based medicine was formally defined in 1966 by Dr David Sackett, a professor of epidemiology at McMaster University, as “the conscientious and judicious use of current best evidence from clinical care research in the management of individual patients.” The basic idea has ancient roots. Anecdotal clinical recommendations had been passed on for centuries; then, from the mid-1600s, physicians’ personal journals then textbooks became sources for sharing knowledge. Peer-reviewed journals were the next messengers of clinical information. In the mid-1900s their content was extracted in the now-defunct Index Medicus. Today the Internet provides easy access to a mountain of up-to-date information; now the problem is sorting through what is presented as fact-based evidence.
Linguists suggest that the word fact has undergone changes in its meaning over time, but since the 16th century the common definition has been “something that has really occurred or is the case.” Today a scientific fact is an objective and verifiable observation. Evidence, in this context, is a collection of facts in support of a conclusion. Experts may be needed to interpret evidence, but that differs from the idea of an “expert opinion.” Attention has to be focused on the evidence presented and not on the expert’s opinion. If an expert offers an opinion without describing the basis for his or her conclusion, it is not possible to know the value of the information. In addition, an expert may have conflicts of interest with certain conclusions or opinions—perhaps in areas of research funding, publication, professional or institutional loyalties, or financial interests.
There is a substantial difference between evidence-based medicine in clinical practice versus public health practice. Facts collected and evidence presented in clinical situations are largely based on randomized controlled trials. Also, clinical trials usually refer to one particular area in therapeutics or diagnostic measures. Population-based studies in public health require data from a list of potentially important interventions within communities. These studies often require longer time periods for study, which in turn requires more effort and resources. Also, comparison groups or communities are often unavailable for randomized studies. Social, economic, and political pressures may delay or influence continuation of studies or presentation or interpretation of findings. In so-called peaceful times these complexities or delays seem to be part of community politics and may be tolerable, even if not advisable. However, delays in enacting certain public health measures in the context of the near-emergency state of our current pandemic may mean a rise in mortality rates that are not tolerable. A hybrid solution to evidence-based public health guidelines may be required.
On one hand, development and administration of safe vaccines must follow the rule of fact-based evidence. Popular requests for mass administration of certain medications must be rejected if they do not pass fact-based evidence of their effectiveness. On the other hand, rules of evidence may be modified for the guidance of certain social behaviors. Measures that are likely to be beneficial—quarantine times, physical distancing, wearing masks, or closing public functions—may be implemented and the evidence of their value collected thereafter. Instead of evidence-based practice, this practice-based evidence would determine the eventual public health recommendations.
In the current emergency state of the clinical and public health situation in many countries, it is more important than ever to provide expert guidelines by following rules. In clinical practice we must insist on fact-based evidence, but in specific aspects of public health actions, post-hoc practice-based evidence may suffice. In all situations, we must ensure honesty when providing assessment and guidance.
—George Szasz, CM, MD
Greenhalgh T. Will COVID-19 be evidence-based medicine’s nemesis? PLoS Med 2020. doi: 10.1371/journal.pmed.1003266.
Schunemann HJ, Zhang Y, Oxman AD. Distinguishing opinion from evidence in guidelines. BMJ 2019;366:14606.
Thoma A, Eaves FF. A brief history of evidence-based medicine (EBM) and the contributions of Dr David Sackett. Aesthet Surg J 2015;35:NP261-263.
This post has not been peer reviewed by the BCMJ Editorial Board.