The evidence house: How to build an inclusive base for complementary medicine

We all want good evidence available when making medical decisions. Evidence, however, comes in a variety of forms and purposes, and what may be good for one purpose may not be good for another. The term “evidence-based medicine” (EBM) has become almost a cliché in recent years, being used as a synonym for “good” or “scientific,” both to support and refute the value of complementary medicine practices.¹ But EBM takes a narrow view of what constitutes “good” evidence, and it excludes important qualitative and observational information about the use and benefits of complementary medicine.

The key idea of EBM is a “hierarchy of evidence” (figure 1). In this hierarchy, information from systematic reviews of randomized controlled trials is the “best” evidence, followed by individual randomized controlled trials, then by nonrandomized trials, observational studies, and finally case-series.² When the evidence of what type of medicine works and what type does not is synthesized, the type of emphasis is at the top of the pyramid, and the evidence that is considered inferior is at the lower levels. Clinical experiments that isolate a causal and additive link between a specific intervention and a specific clinical outcome are seen as the “gold standard” in this evidence model.

Figure 1.

The traditional hierarchy of evidence is narrow

As most clinicians know, the reasons that patients recover from illness are complex and synergistic, and many cannot simply be isolated in controlled environments. The best evidence under these circumstances may be observational data from clinical practice that can estimate the likelihood of a patient's recovery in a realistic context.³ In addition, patient's illnesses are complex physical, psychological, and social experiences that cannot be reduced to single, objective measures.⁴ In some cases, the most valuable information for a clinical decision is a highly subjective judgment about life quality. This personal experience of illness might be captured only through qualitative research, not using questionnaires or results of blood tests.⁵ The “best” evidence under these circumstances may be the meaning that patients give to their illness and recovery.

At other times, the “best” evidence comes from laboratory studies. The discovery that St John's wort can reduce blood levels of immunosuppressive drugs, for example, is the most crucial evidence when making decisions about its use in patients taking immunosuppressive medications.⁶ Findings of controlled trials often do not reveal such drug interactions. Arranging types of evidence in a “hierarchy” obscures the fact that sometimes the best evidence is not objective, not additive, and not clinical.⁷

In the place of an evidence hierarchy, I suggest we build an “evidence house” with “rooms” for different types of information and purposes (figure 2). The rooms on the left side of the house contain types of information that seek out causal attributions and mechanisms of action. One such room is for laboratory research, which forms a foundation of understanding of mechanisms and causal links on which controlled clinical research can build. In the case of homeopathy or prayer, for example, randomized controlled trial data seem to point us in an illogical direction, eg, that pills with no active ingredients have specific effects.⁸ Other rooms on the left side of the house are for randomized controlled trials and systematic reviews, which attempt to verify the suspected links between specific interventions and specific outcomes.

Figure 2.

The evidence house affords greater accessibility to important information

If confined to the left side of the evidence house, however, physicians will never obtain information about the relevance of medicine for patients, what happens in the actual world of clinical practice, or the generalizability of an intervention in our health care delivery system. Information about relevance and utility of practice, both proven and unproven, is available in rooms on the right side of the house.

The evidence house has something for everyone. Regulatory agencies and those interested in the approval of new treatments are most interested in the rooms on the left side. They want data from randomized controlled trials and systematic reviews rather than findings from observational research, yet the need for alternative approaches to treatment is evident.⁹ Other stakeholders in the health care system are more interested in information from the right side of the house. Health care practitioners often want to know the anticipated effects of an intervention in the clinical practice setting. Those paying for care are generally more interested in health services research. Patients are intensely interested in stories and detailed descriptions of cases similar to their own.¹⁰

If resources are disproportionately invested in certain rooms of the house to the neglect of others, it is not possible to obtain the evidence needed for full public participation in clinical decisions. A livable house should not have an elaborate kitchen and no bathroom. Each has different functions and all need to be high quality.

Complementary and alternative medicine helps us think about who will live in the evidence house and how it should be constructed. The public is the architect, driving the interest in complementary medicine. They seek holistic and preventive care, safer treatments for chronic illness, and more participation in health care decisions.¹¹ As patient advocates, physicians must help them find a seat at the research table, so it is possible to build an evidence house where everyone can live.