Evidence Based Medicine

First published in The Lawyers Weekly April 4, 2003, Vol. 22, No. 45

The first decade of Evidence Based Medicine (EBM) has given Personal Injury and Medical Malpractice lawyers both benefits and headaches.

Expert opinion is moving away from a trial of strength between medical “authorities” and towards structured dialogue about a universally accepted body of empirical evidence.

A useful definition of Evidence Based Medicine is “the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients.”

Even the most enthusiastic champion of EBM will acknowledge that medicine is an art as well as an inexact science. Good doctors use both individual clinical expertise and the best available external evidence, and neither alone is enough.

Older physicians learned authoritarian medicine rather than problem-based medicine. They may consequently find it more of a challenge to evaluate the new evidence and manage the uncertainty that a rapidly changing body of knowledge generates.

One of my mentors would point out that history has showed repeatedly that about 50% of medical beliefs will subsequently prove to be incorrect. The trick is to know which 50%.

The main types of clinical research evidence in increasing order of reliability - and decreasing order of abundance - are case reports, case series, case-control studies, cohort studies, systematic reviews and meta-analyses.

Case reports are the weakest clinical evidence for causation. They may nevertheless be invaluable in alerting clinicians to previously unrecognised associations, as occurred with limb deformities and Thalidomide given to the mother during pregnancy.

Case series give a more reliable indication of trends. If Fibromyalgia Syndrome occurs more after 100 consecutive soft tissue neck injuries than after 100 consecutive leg fractures, the effect is more likely to be real than if it there are only half-a-dozen individual reports in the medical research literature.

Nevertheless, supposed causal connections may prove spurious on more critical analysis. Case-control studies attempt to remove confounding variables. This they do by looking at differences between a population of patients and a population of patients or healthy individuals who are pair-matched except for the feature being studied.

Cohort studies remove further selection bias by following sufficiently large normal populations over time to track the appearance and progress of disease processes. Whether Low Back Pain is caused by a rear-ending MVA can be determined only by studying the spontaneous appearance and disappearance of the symptom in an otherwise healthy, uninjured population.

Huge population cohorts must be studied to determine whether major trauma precedes the onset of multiple sclerosis.

Systematic Reviews (MedLine keyword “Cochrane”) evaluate the strengths and weaknesses of all relevant research to date, and allocate a reliability score to the strength of evidence for a given proposition. Only 4 studies of bedrest for acute Low Back Pain or sciatica proved to be of high research quality, and they showed little or no benefit compared with advice to stay active.

Meta-analysis involves the statistical manipulation of data from all available quality studies which contain sufficient detail. By combining the populations studied by each researcher, spurious and anomalous findings are eliminated, and trends which are not statistically significant in an individual study may prove to be valid. Although individual studies give conflicting results, cognitive therapy in mild to moderate depressive disorder has superior effects compared with antidepressant medication.

Academic physicians with some knowledge in a given area, and particularly those with only limited knowledge of a subspecialty, are better than "the authorities" at evaluating the research evidence, and they reach greater consensus about the conclusions which should be drawn. The personal biases and memorable clinical experiences of an "authority" may distort a more complete and balanced view of both causation and prognosis.

Traditionally, the courts have accepted the personal experience of credible expert witnesses and the opinions of recognised “authorities”, but the climate of medical opinion will increasingly favour instead the conclusions of well-designed clinical research.

This democratisation of medical expert evidence means that legal counsel can more transparently challenge medical experts during cross-examination. Such confrontation requires considerable immersion in medical concepts, terminology and controversies, but the medical expert can no longer take a condescending, dismissive stance behind a cloak of “authority”.

Three common criticisms of EBM highlight universal problems in the practice of medicine.

1. Shortage of coherent, consistent scientific evidence

There is little or no empirical evidence for the effectiveness of most passive physiotherapy in accelerating healing. What is perhaps more alarming to lawyers as counsel (and as potential patients) is that the same generalisation can be made about the majority of traditional medical treatments. Indeed, there is more empirical evidence for the effectiveness of common prayer and private meditation than for most standard therapies.

2. Difficulties in applying evidence to the care of individual patients

There is a wealth of biological variation between individual patients/clients, including those who have suffered a particular injury or illness. More important perhaps, clinical research attempts to answer questions with more certainty by excluding as experimental subjects those patients who have additional medical conditions that might complicate the pathology being studied. The reality is that most claimants and plaintiffs do have co-morbidity, and different medical conditions do interact with each other.

3. Cook-book medicine

Threats to curtail clinical freedom cause some physicians to bristle. Indeed, the idiosyncratic application of unorthodox therapies has frequently triggered major medical breakthroughs. Nevertheless, the movement to eliminate useless treatments that are useless, expensive and potentially dangerous long preceded this first decade of Evidence Based Medicine.

Evidence Based Medicine is a young child that will continue to grow. At times clumsy and gawky, EBM will continue to embarrass both physicians and lawyers in the courtroom. Healthy and vigorous, it is a force to be reckoned with.