Wednesday, September 8, 2010

"Clinical Decision Making: Evidence Is Never Enough"

A senior resident, a junior attending, a senior attending, and an emeritus professor were discussing evidence-based medicine (EBM) over lunch in the hospital cafeteria.

"EBM," announced the resident with some passion, "is a revolutionary development in medical practice." She went on to describe EBM's fundamental innovations in solving patient problems.
"A compelling exposition," remarked the emeritus professor.
"Wait a minute," the junior attending exclaimed, also with some heat, and presented an alternative position stating that EBM merely provided a set of additional tools for traditional approaches to patient care.
"You make a strong and convincing case," the emeritus professor commented.
"Wait a minute," the senior attending exclaimed to her older colleague, "their positions are diametrically opposed. They can't both be right."
The emeritus professor looked thoughtfully at the puzzled physician and, with the barest hint of a smile, replied, "Come to think of it, you're right too."

So begins the Users' Guide to Medical Literature issue #XXV, "Principles of Applying the Users' Guides to Patient Care", published 10 years ago, almost to the day in JAMA (JAMA 2000;13:284;1290-6). I am enjoying re-reading it, as I now appreciate the authors' evolving positions acknowledging the complexities of modern practice and the need to hold together apparent dualities. They acknowledge their continued commitment to the scientific rigor of EBM:
In 1992, in an article that provided a background to the Users' Guides, we described EBM as a shift in medical paradigms.2 In contrast to the traditional paradigm, EBM acknowledges that intuition, unsystematic clinical experience, and pathophysiologic rationale are insufficient grounds for clinical decision making, and stresses the examination of evidence from clinical research. The philosophy underlying EBM suggests that a formal set of rules must complement medical training and common sense for clinicians to effectively interpret the results of clinical research. Finally, EBM places a lower value on authority than the traditional paradigm of medical practice.
However, they point out that the complexities of the world often call for more than one way of approaching problems:
While we continue to find the paradigm shift a valid way of conceptualizing EBM, as the scenario suggests, the world is often complex enough to invite more than 1 useful way of thinking about an idea or a phenomenon. In this article, we describe the 2 key principles that clinicians must grasp to be effective practitioners of EBM. One of these relates to the value-laden nature of clinical decisions; the other to the hierarchy of evidence postulated by EBM. 
A few paragraphs into the paper, we come to a surprising heading, which serves as the title for today's post: "Clinical Decision Making: Evidence Is Never Enough". Wow, is this not a bit heretical, especially coming from the cradle of EBM? What do the authors mean by this? To illustrate this they develop three scenarios, each involving a patient with pneumococcal pneumonia, a disease for the treatment of which plenty of strong evidence exists. Yet, depending on the context of the patient's situation, treatment decisions may or may not be straightforward. Their examples of a terminal cancer patient who herself may forgo treatment, an elderly demented nursing home patient with no family, whose treatment decisions have to be made solely by the clinicians, and a 30-year-old mother of two, whom only Lord Voldemort would consign to non-treatment. The point being that evidence of effectiveness, in this case for the treatment of pneumococcal pneumonia, is necessarily applied to the particular circumstance at the bedside. In other words, some value judgments are employed to apply the existing evidence to a trade-off decision. Quantifying this process is far from a clear science:
Acknowledging that values play a role in every important patient care decision highlights our limited understanding of eliciting and incorporating societal and individual values. Health economists have played a major role in developing a science of measuring patient preferences.14-15 Some decision aids are based on theassumption that if patients truly understand the potential risks and benefits, their decisions will reflect their preferences.16 These developments constitute a promising start. Nevertheless, many unanswered questions concerning how to elicit preferences, and how to incorporate them in clinical encounters already subject to crushing time pressures, remain. Addressing these issues constitutes an enormously challenging frontier for EBM.
Switching gears somewhat to delve into some of the pragmatic issues, the authors talk about the hierarchy of evidence, acknowledging the superiority of systematic clinical observation over ad hoc anecdotal evidence as a tool to reduce common threats to inference validity. However, they loudly and clearly state that in practice one size does not fit all:
Clinical research goes beyond unsystematic clinical observation in providing strategies that avoid or attenuate the spurious results. Because few, if any, interventions areeffective in all patients, we would ideally test a treatment in the patient to whom we would like to apply it. Numerous factors can lead clinicians astray as they try to interpret the results of conventional open trials of therapy, which include natural history, placebo effects, patient and health worker expectations, and the patient's desire to please.
... and offer the following hierarchy of evidence for individual treatment decisions:

Table 1. A Hierarchy of Strength of Evidence for Treatment Decisions
So, for a patient encounter, the most robust kind of evidence is the N of 1 trial! Not too coincidentally, I came to the same conclusion here. With a few caveats, the authors confirm the feasibility of this undertaking:
N of 1 RCTs are unsuitable for short-term problems; for therapies that cure (such as surgical procedures); for therapies that act over long periods of time or prevent rare or unique events (such as stroke, myocardial infarction, or death); and are possible only when patients and clinicians have the interest and time required. However, when the conditions are right, N of 1 RCTs are feasible,24-25 can provide definitive evidence of treatment effectiveness in individual patients, and may lead to long-term differences in treatment administration.26
They go on to say that applying results based on group data may be fraught with erroneous assumptions:
When considering any source of evidence about treatment other than N of 1 RCTs, clinicians are generalizing from results in other people to their patients, inevitably weakening inferences about treatment impact and introducing complex issues of how trial results apply to individuals.
They again stress the importance of the individual encounter and making collaborative decisions in the context of the patient's values:
Thus, knowing the tools of evidence-based practice is necessary but not sufficient for delivering the highest-quality patient care. In addition to clinical expertise, the clinician requires compassion, sensitive listening skills, and broad perspectives from the humanities and social sciences. These attributes allow understanding of patients' illnesses in the context of their experience, personalities, and cultures.
They rightfully treat scientific evidence as the foundation of practice, but not the whole of it. Indeed, they conclude that
A continuing challenge for EBM, and for medicine in general, will be to better integrate the new science of clinical medicine with the time-honored craft of caring for the sick.
I really like the tempered tone of this paper, paying homage not only to the science, but also to the art of medicine. It is clear that the authors have evolved with the field, and if these giants can evolve, so can we. Clearly, in the art of medicine, "evidence is never enough".




  1. These last three posts have been wonderfully lucid and enlightening for a semi-lay person like me. I hope they are widely distributed among physicians, academics, and policy makers. I hope they have an effect!