What is evidence-based medicine?

Over the past four decades, the international medical community has increasingly moved away from a paternalistic, ‘doctor knows best’ model of ‘authority’ or ‘eminence’ based medicine. It generally now subscribes to the principles of evidence-based medicine (EBM) described above. EBM involves using the most up-to-date information from well-conducted clinical research to inform patient care, precisely because we can be ‘fooled’ by our biases, and what we see in front of our eyes.

Clinicians nowadays are expected to keep in touch with new developments in medical research in their field, and to be able to critically appraise and use this information in practice.  To meet this need, methods have been developed to summarise, quantitatively combine (where appropriate), and evaluate all the research evidence that has been generated to answer a particular question.  This is called systematic review and meta analysis.  Methods have also been developed to appraise the quality or certainty of evidence.  A popular set of methods for this is known as the GRADE approach. (GRADE Working Group, 2020)

To decide what the best treatment is for a given patient or group of patients, clinicians and policy makers often rely on guidelines, which are usually produced by multidisciplinary groups of clinicians, researchers, methodologists and patient stakeholders, sometimes with input from specialists in health economics and public health or ethicists. Guidelines can be produced or adapted locally, nationally or are written for a global audience (e.g. World Health Organisation guidelines). Traditionally, guidelines used to be written by ‘experts’ based on their opinions about best practice. Although some ‘consensus’ might be better than no guidance at all, this approach has also been labelled GOBSAT (‘good ‘ole boys sitting around a table’). Guidance without proper EBM methodology suffers from being biased, often ignores population and primary care data, tends to be driven by the ‘tip of the iceberg’ expensive secondary sector and influenced by vested interests. In the EBM era, evidence-informed guideline processes are increasingly seen as the best approach, especially when patients can be shown what is known about the sizes of risks and benefits in shared decision aids and asked about what they value. These guidelines are developed open-mindedly with pre-specified questions and come to transparent conclusions. The GRADE approach is increasingly used to link systematic reviews of evidence, make explicit judgements about the certainty of the evidence, and elicit other important factors, including the likely balance of benefits and harms, to determine recommendations for practice (or recommendations for research if the evidence base is too poor). The aim of these methods is to help the people writing guidelines to make good decisions that take into account all the important information, and to set out their decision-making clearly and transparently for people using the guidelines. (Alonso-Coello et al., 2016)

There has been criticism surrounding these methods as some clinicians do not agree that evidence based medicine is always a good thing. Some rightly note the limitations of what can be discovered by conducting randomized controlled trials (RCTs), and the difficulty of applying average results from trials involving hundreds of people to individual patients with specific needs. Others have expressed concern that over-reliance on EBM might undermine the experienced clinician’s ability to apply the knowledge they acquire through years of practice. (Greenhalgh, Howick and Maskrey, 2014) This might particularly be the case when treatment effects are small and when the illness is not well defined. In the field of psychological therapies, achieving the ‘Gold Standard’ of the RCT is especially difficult. Although not entirely unfeasible, trials for psychotherapy pose significant challenges for study design, for example around double-blinding or appropriate outcome measurements.

Nevertheless, when used judiciously, clinical guidance can help train staff, improve outcomes and contain costs. As a previous Chair of NICE stated, recommendations should be seen as “guidelines, not tramlines.” (McCartney, 2014) They are not as detailed as textbooks, and decisions about care must be logical and individualised for each patient.

EBM has simultaneously become a quality mark in the medical literature and in the production of guidelines. This means that parties with a vested interest in producing a particular result or recommendation might misuse the methods; either in the way they design or conduct trials, or in the way they use evidence to make guidelines. Typical examples occur when the definitions of disease change (‘mission creep’), when for-profit corporate pharmaceutical or kit companies run studies using favourable, short term, proxy endpoints, or the data is interpreted in a biased way by a doctor with a special interest or private practice. Not everything that calls itself ‘evidence-based’ is really based on the best evidence interpreted appropriately. Doctors have to get more savvy at critical analysis.

References:

Alonso-Coello, P. et al. (2016) ‘GRADE Evidence to Decision (EtD) frameworks: a systematic and transparent approach to making well informed healthcare choices. 1: Introduction’, BMJ, 353, p. i2016. doi: 10.1136/bmj.i2016.

GRADE Working Group (2020) The Grading of Recommendations Assessment, Development and Evaluation working group. Available at: https://www.gradeworkinggroup.org/.

Greenhalgh, T., Howick, J. and Maskrey, N. (2014) ‘Evidence based medicine: a movement in crisis?’, BMJ, 348(jun13 4), pp. g3725–g3725. doi: 10.1136/bmj.g3725.

McCartney, M. (2014) ‘Margaret McCartney: Have we given guidelines too much power?’, BMJ, 349(oct06 1), pp. g6027–g6027. doi: 10.1136/bmj.g6027.

Sackett, D. L. et al. (1996) ‘Evidence based medicine: what it is and what it isn’t’, BMJ, 312, p. 71. doi: 10.1136/bmj.312.7023.71.