INTRODUCTION AND OVERVIEW

This chapter covers some of the generic issues related to evidence-based medicine (EBM), with particular emphasis on how these apply to integrative general practice and complementary therapies. Although EBM principles are a vital part of the armamentarium of the modern doctor, they are a two-edged sword.

MEDICAL OPINION VERSUS EVIDENCE

Traditionally, doctors in training have looked to ‘expert opinion’ from senior medical staff as their primary source of guidance on clinical decision-making. Their long experience and learning from prior generations of medical experts was deemed sufficient authority and was rarely questioned. Then the general practitioner (GP) would also add their personal clinical experience as it was gathered over the years to formulate and adapt their particular approach to clinical problems.

As simple and intuitive as this approach is, it has always had deficiencies. Our perceptions, attitudes and range of options can be informed by expert opinion, but equally they can be limited or biased by them. A recent study concluded that:

Put another way, when we are confident of our opinions, and have had them handed down to us from respected authorities without question, and when we are not questioned about the validity of our opinions, we are less likely to determine whether they are based on evidence.

POTENTIAL AND LIMITATIONS OF EBM

As history is written, the exponential growth in EBM gained momentum in the late twentieth century. Published data increasingly revealed:

The Cochrane Collaboration was formed out of this movement, and its systematic reviews follow a transparent process ‘intended to minimise bias’. We accept this as almost a motherhood statement, but the processes inherent in EBM contain a number of major flaws.

In recent decades, EBM has rightly assumed a leading role in informing medical practice. Stratifying and analysing the results of all published trials for a disease or an intervention provides some guidance on the three pillars—quality, safety and efficacy—and allows for comparisons to be made. To make clinical decisions and formulate clinical guidelines that are contrary to evidence is at best ineffectual and wasteful of resources, and at worst harmful to the patient.

However, a bland statement that the clinician should make decisions that are evidence-based is not as simple as it seems, for a number of reasons.

Some particular limitations of EBM in the general practice setting are summarised by Stephenson:²

It is for these reasons that the best approach to clinical decision-making will combine knowledge of the best available evidence with:

Many complementary therapies are particularly affected by the points raised above. Naturally occurring products, for example, are not patentable, and so they don’t attract the large research budgets that patentable pharmaceuticals do. Even where there is mounting evidence that a particular complementary therapy is safe and effective, it is often treated with scepticism by the medical mainstream because it falls outside the imaginary boundary of conventional medical practice. As clinicians we need to be interested in what is safe, works and is cost-effective regardless of which side of an artificially created demarcation line between complementary and conventional therapies it comes from.

LEVELS OF EVIDENCE

EBM experts tend to refer to the ‘level of evidence’ for or against a particular therapy or intervention. Broadly speaking there are four main levels of evidence, although there are subdivisions within these:

Obviously, level 1 evidence is considered the highest; the relative weight given to each of the others diminishes as you go down the levels. In reality, however, it is not as simple as this. For various reasons, some interventions or issues do not lend themselves to RCTs or cannot attract the necessary funding for high-quality RCTs and will therefore never have level 1 evidence supporting them. This does not mean that they are invalid, but simply that one needs to be flexible in interpreting evidence and that EBM needs to be supported by common sense and clinical experience.

Meta-analyses also rely on the publication of all available studies. Because publication bias is more likely to exclude negative findings, meta-analyses of published studies tend to skew to positive findings.

EBM reviews sometimes provide challenging findings. For example, a meta-analysis published in The Lancet gave surprising results on the efficacy of homeopathy, finding that the odds ratio for positive trial results was 2.45 in favour of homeopathy.³ Though more high-quality RCTs are required, either homeopathy is clinically effective for a range of conditions or there is a publication bias in favour of homeopathy. Thus, even with ‘level 1 evidence’ a clinician still needs to interpret the findings and decide what to make of them.

Patients and the general public are often not aware of levels of evidence, and nor can they easily interpret evidence for themselves. Furthermore, they can be significantly affected by misleading marketing. The GP therefore has a vitally important role in helping people to: