Understanding Evidence-Based Medicine

Evidence-based medicine (EBM) is the practice of integrating clinical experience and patient values with the best available research information to optimize patient outcomes.

A healthcare provider concluding on a clinical decision through EBM can be akin to a financial analyst concluding on a business model. A balance sheet of benefits and harms is drawn up based on a combination of research findings and the patient's unique circumstances and the clinician then makes an informed decision in the best interest of the patient's outcome.

Incorporating the best available research information is key to EBM decision-making and involves four essential steps:

1.      Asking answerable questions

2.      Accessing the best information

3.      Appraising the information obtained for validity and relevance

4.      Applying the information to specific patient care

In asking answerable questions, it is paramount to frame the clinical question appropriately. Information needs analysis has revealed an average of 1-2 questions arise for each outpatient consultation while the figure can go up to 5 for each inpatient consultation. About a third of questions will relate to treatment of a specific condition while a quarter will relate to diagnosis. Background questions that address basic physiological processes are best left to textbooks to answer while foreground questions that relate to clinical decision-making are best facilitated by EBM. Framing a good question to be answered is accomplished by defining a population with a clinical problem, the intervention or exposure to the population, a suitable comparator for the intervention, and the outcome variables to be assessed. An example of a patient's clinical question that relates to EBM may be rephrased as "In asymptomatic adult women at average risk of breast cancer (population), does screening at a cancer clinic (intervention) reduce the likelihood of breast cancer fatality (outcome) compared with routine self-examination (comparator)?"

In accessing the best available information, summarized primary (new studies and findings) research sources like evidence-based guidelines and systematic reviews are of the highest value. The ideal information source should have high quality data, be clinically applicable, be comprehensive and be user-friendly. Should the important summarized information be unavailable, the next best option is to access the primary research itself. The most common filter of primary research called MEDLINE, PubMed is available online.

EBM is modeled on levels of evidence that relate to the way primary research is carried out. The "prospective, double-blind, randomized, controlled" study is often hailed as the gold standard upon which clinical evidence is generated. A prospective study involves following the study group over a period of time. Double blinding in a study involves the subject and the researcher not being aware of the identity of the intervention. Randomization involves reducing bias in the choice of subjects for the study. The control is often a placebo but can also be the currently available standard of treatment thereby adding further weight to the intervention outcomes. At the lower rungs of evidence, studies would only consist of case reports and other anecdotal comments.

Once research information is gathered, this needs to be appraised for quality and relevance. Poor quality studies have been known to overestimate the benefits of interventions by 30% or more and this can make actually ineffective interventions seem effective. The clinician practicing EBM at this stage has to query how strong the evidence is, how big the effect is and whether the effect matters to patients. The statistical precision of results is often important as it points to whether the study's findings can be explained by chance.

The last stage to EBM decision-making is for the clinician to decide on whether the best available research can relate to the individual patient's situation and if so, how the research can best determine the course of action to take in diagnosing or treating the patient. A balance sheet of benefits and harms of the intervention is first drawn up after which the likelihood of the benefits and harms are quantified in relative terms. These relative terms are then converted into absolute terms based on the patient's individual characteristics. The final stage of the clinical decision in diagnosis or treatment then rests with whether the individualized benefits outweigh the individualized harms.

In adopting the EBM approach, clinicians sometimes cite insufficient time, limited search skills and limited access to evidence as impeding their use of the best research information. In most practical clinical situations, EBM is a core foundation upon which sound decisions can be made. Nevertheless the final decision also hinges on the clinical experience of the healthcare provider, the individual patient's values as well as the costs of the diagnosis or therapy. The clinical experience of the healthcare provider remains crucial to patient outcomes especially should there be a highly urgent clinical situation, a distinct lack of useful research information available or the patient circumstances are unique beyond the direct applicability of research information.

New tools and support structures however, are rapidly becoming available to assist clinicians in adopting EBM. These include newer and more sophisticated computer software and clinical decision support tools along with mobile hardware that clinicians can carry along to better practice EBM at points of patient care. Several initiatives are also ongoing in encouraging the greater adoption of EBM in practice. At the forefront is the Cochrane Collaboration, which develops systematic reviews. Other proponents of EBM include Bandolier, McMaster University, the Centre for Evidence-based Medicine, the Evidence-based Medicine Resource Centre as well as other prominent government and non-profit organizations.

EBM works in the best interest of patients to complement the experience of clinicians in delivering the best outcomes. When adopted appropriately, EBM serves to make the healthcare experience safer and more cost-effective.