Тhe definition of evidence-based medicine. The history of evidence-based medicine

The origin and basic concepts of evidence-based medicine. The concept of "Evidence-based medicine": terminology of EBM. Levels of evidence and grades of recommendation. The world experience of development. Hierarchy of evidences of information sources.

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«Тhe definition of evidence-based medicine. The history of evidence-based medicine. The world experience of development»

Origin of evidence-based medicine

When consider situation in medicine of XX century you may notice that huge mass of information such as new books, journals have been descended on doctors, there has been appeared the monster of information - Internet. As far broader expansion of new information technologies (electron databases and journals, multimedia educational programs on optical disks and Internet) as abilities of doctors to obtain most operative information are constantly expanded. Naturally that necessity to conceive possibilities of these technologies, determine it place, role and relationship with traditional printed publications has been appeared.

Good doctor always aspires to be well informed about last achievements of medicine. Searching answer on clinical problem doctor may use different sources of information and gets different sometimes mutually exclusive one another recommendations. Such findings don't solve problem but aggravate it.

Now pharmaceutical market counts more than 20 thousands of drugs. And aggressive marketing of pharmaceutical firms, massive impact of TV-programs made by non-competent in medical questions authors on consumers of drugs is seen on this background. In the result both doctor and patient turn out difficult position as for the treatment of diseases several methods of treatment are proposed and all of them, as claimed in those sources, are the best. How in this situation distinguish less reliable information from a truly accurate and objective?

For example, a small digression into the history of medicine shows that the search for answers to such questions stirred the minds of many prominent scientists and even people without any relation to medical science, long before, as in the 1990's the term "evidence-based medicine" had appeared (EBM).

It is known that the Roman Emperor, King of Sicily and Jerusalem, Frederick II (1192-1250) interested how exercise can affect digestion. To clarify this, he ordered to give the same food two knights and one was send to hunt, and another - to sleep. A few hours later they had slain, and examined the contents of the digestive tract. It turns out that digestion in stomach of sleeping knight act more intensively.

In the XVII century physician and philosopher, Jean Baptist van Helmont proposed the first clinical trial involving a large number of participants, with their randomization and statistical analysis to evaluate the usefulness of the practice of bloodletting. It was supposed involvement in the research 200-500 poor people with the division of them into 2 groups by drawing lots, where in one group phlebotomy would not performed, and in another - bloodletting has done as much as the doctors deemed it necessary. To assess the effectiveness of bloodletting assumed the number of funerals in each group, but, unfortunately, history has no data on the implementation of this experiment.

In the middle of the XIX century in Paris in his works, Pierre Charles Alexander Louis described the principles of statistical analysis to evaluate medical treatment and showed that bloodletting is unhelpful kind of treatment. True, it has not changed the habits of physicians at that time and during subsequent phases of the history of mankind. This problem - transfer (translation) of research findings into practice - remains valid today.

In 20-ies of the XX century, Ronald Fisher first introduced the principles of statistical planning and analysis of experimental studies. After the Second World War, through the work of the Austin Bradford Hill and his followers, the British epidemiologists Richard Doll and Archibald Cochrane, this area of science began to have a significant impact on clinical practice and public health.

Finally, to the curtain of the XX century, with the joint efforts of more than fifty professionals, primarily from Canada's McMaster University, as well as from other universities and institutions of different countries, basic principles of evidence-based medicine were justified.

As in real medical practice in solving problems relating to treatment of specific patients, physicians often can not eliminate doubt of loyalty to their judgments, in the result not all his actions are correct (in the sense relevant to the current level of scientific knowledge). At the same time for different tactics of health care and clinical outcomes may be the same. Understanding that the treatment should be assessed on the final outcome (clinically important, important for the patient) has come from the cumulative experience of clinical medicine and development of clinical epidemiology. This is the key moments of the concept of evidence-based medicine.

EBM from way of thinking of the group of advanced physicians and epidemiologists has transformed into a variant of the standard medical practice. Moreover, the principle of evidence occupied a key place in the evaluation of medical technologies, and not only in relation to the management of patients, but also to management decisions and financing. Now it is obvious that this transformation extends far wider than medicine, covering all areas of human activity.

Knowledge of basics of evidence-based medicine, which in the past 10-15 years, developed very rapidly, became absolutely necessary for researchers and physicians, because facilitates clinical decisions making.

Basic concepts of evidence-based medicine

People always inclined to believe in thing not proven

but to their taste.

Blez Pascal

The deepest sin against the human mind

- believing the unproven.

Thomas Haksly (1825-1895)

By the last quarter of the twentieth century there was a situation where every 5 years, the volume of medical information has doubled, and experts do not actually have time to get acquainted with it for use in daily practice. In order to assist physicians in the study of clinical research findings for practical application, a group of epidemiologists from the University of McMaster led by David Sackett wrote a series of articles published in medical journals, beginning with the series, published in the Canadian Medical Association Journal in 1981 and later.

The authors used the term “critical evaluation” (critical appraisal) to designate critical of the medical literature by doctors trained to assess the quality of research. Later they became convinced of the need for large-scale program to teach physicians to use the information to solve problems in the treatment of individual patients. Then the process of practical application of the published data in the literature D. Sackett called the "transfer of critical appraisal to the bedside." Now realized that getting research results in basic medicine, and even in clinical medicine, not to scientific advances were part of everyday practice needs systematic efforts to transfer into practice, "translation" of language study in language practice. This area of research and practice referred to as transfer (broadcast).

The term "evidence-based medicine" was used in 1990 in the newsletter for entering residency training in internal medicine at McMaster University. It said: "In everyday use the methods of diagnosis, treatment and prognosis residents must adhere to an enlightened skepticism. EBM approach is a thorough study of current scientific evidence and assessing their validity and practical significance. A doctor should be able to clearly articulate the clinical question, searching for an answer to it in the medical literature, to conduct a critical assessment of the facts found, to determine the possibility of their use in treating a particular patient and directly apply the data found in practice ".

In 1991, the term "evidence-based medicine" appeared in the pages of the new magazine ACP Journal Club. In those years continue to be developed the practical implementation of the principles of EBM and teaching her the basics. Also established an international working group on preparation of materials to familiarize physicians with the principles of the practical application of this medical literature.

The result of their work became the birth of a series of articles under the title "The recommended approach to the study of medical literature (reader's guide), which were published in JAMA in 1993, these articles have been collected in the most complete edition of EBM, published in Russian and accessible on the Internet (http://www.cche.net/ usersguides / main.asp).

EBM is the way medical practices that differentiate the most reliable information for medical decisions. The main objective of the EBM - the constant improvement of the efficiency of medical services for diagnosis, treatment and prevention of diseases, as well as the introduction of means leading to the rational use of scarce resources.

EBM uses to achieve a relatively young science and clinical epidemiology. Clinical epidemiology (CE) is developing a scientific basis of medical practice. The central tenet of FE: every clinical decision should be based on strict scientific grounds. This is the «evidence-based medicine», the literal translation - "medicine based on evidence" or, more accurately reflects the meaning of the term "evidence-based medical practice" or "scientific evidence-based medicine."

The concept of "Evidence-based medicine" means the following:

guarantee the most effective and safe treatment, based on the best available evidence;

data collection, interpretation and integration of reliable clinical data derived from observations of experts and in tests, reports of patients;

search technology, analysis, synthesis and application of medical information, allowing to make better clinical decisions;

process of continuous self-managed learning, which allows to integrate the most reliable of the existing evidence from individual experience;

new paradigm of clinical medicine, which differs from the previous less impact on subjective selection criteria for the diagnosis and therapy requires a doctor's critical assessment of the views of various experts and the results of clinical studies;

information technology for determining the optimal choices of medical practice.

By definition of well-known experts, EBM - deliberately and consistently use the best proven results of clinical trials in the treatment of individual patients. Used in this definition have the following values.

Intentional: deliberate application of research results to each patient.

Consistent: the account in each clinical case, the ratio of risks and benefits of the treatment method used, taking into account the uniqueness of each patient, including his general condition, comorbidities, and preferences.

The best proven results of research: on the basis of a critical approach a specialist chooses the best of the whole range of studies to diagnose or treat a specific disease.

Unbiased predictors of EBM were an increase in volume of scientific medical information, as well as lack of financial resources associated with an increase in health spending. Every year in medical practice are being introduced all the new methods of diagnosis, treatment and prevention. These methods are more or less intensively studied in numerous clinical studies whose results are often disparate and even contradictory. Consequently, a large number of methods to choose the one that have the highest efficacy and safety. It should be remembered that the novelty or the high cost of new interventions are not a guarantee of its superiority over other interventions.

Thus, for use in practice, this information must be carefully analyzed and summarized. EBM methodology involves a critical analysis of all data in order to discard inferior, inconclusive, and based on reliable results obtained with the help of effective research methods.

EBM to date, has significantly changed the ratio to the diagnosis and therapy, as well as for many other diseases have been offered new, more effective interventions. At the same time present evidence of inefficiency, useless or even harm to the health of the patient some of the older procedures.

Now many studies aimed at improving the quality of care carried out. Annually updated database MEDLINE results for about 10 thousand randomized controlled trials (RCTs). In the Cochrane Collaboration Trials Register (The Cochrane Collaboration; http://www.cochrane.org) contains references to approximately 850 thousand of such studies. However, not all findings are being implemented in daily clinical practice. Studies conducted in the U.S. and the Netherlands showed that 30-40% of patients do not receive treatment in accordance with international recommendations, and 20-25% of patients receive treatment that they are not shown.

Introduction of EBM in daily activities is still a doctor and an economic aspect. Even in highly developed countries, the resources allocated by the state for health, not quite meet the needs of society. Therefore, undoubtedly, the most effective direct these resources to the development of methods of prevention, diagnosis and treatment, practical use has been confirmed by studies that meet the criteria of evidence-based medical practice.

When analyzing the results of clinical studies made to evaluate their credibility, based on which are determined by levels of evidence?

Terminology of EBM

* Empirical way of scientific knowledge - knowledge is produced by the experiment or observation.

* Theoretical way of scientific knowledge - knowledge obtained by logical constructs (hypotheses).

* Hypothesis - probable knowledge and can be refuted or confirmed, while a scientific fact - its certain knowledge. As a result, the testing of hypotheses appear scientific facts.

* The scientific fact - the confirmation of the hypothesis as a result of qualitative research.

* The reliability of the data (Internal validity, methodological quality) - depends on the compliance plan for the study goal, on the level of integration and minimize systematic and random errors in the study.

* The systematic error or bias - it is systematic (non-random, one-way), the deviation results from the true values.

* Random error or random variation - to reject the result of observations in the sample from the true value in the population due solely by chance.

* Generalizability of the results (External validity, generalisability) depends on the criteria of inclusion-exclusion, increased during the multicenter study.

Levels of evidence and grades of recommendation

In practice, health care workers can enjoy many potential sources of information about medical interventions:

Materials research conducted by medical professionals or specialists from other fields;

Research materials and other information from the pharmaceutical and other companies;

Overview of research and clinical guidelines;

The opinions of experienced specialists (experts);

The opinions of colleagues;

Their personal experience;

Certificate of patients based on their own experience.

For the physician are most valuable studies published in scientific medical journals. This is explained by the fact that articles in journals undergo rigorous selection and editing, which reduces the probability of getting poor-quality information, or incomprehensible, uninformative message.

In turn, scientific reports in journals do not always represent the results of original research. It may also be comments and discussions. Published in journals, along with medical and biological research, as well as studies performed on animals.

Most information is scientific evidence studies differ in that they represent systematic process that is conducted according to clearly develop a protocol which seek to exclude or explicitly identify their own biases and allow the researcher obtain results that are relevant to patients / clients and medical practitioners working in this area.

Figure 1. Hierarchy of evidences of information sources. It is offered by JR.B. Haynes, here bringing in variant of Sweden council on methodology of evaluation in health care system concerning medical and theraupeutic interventions

evidence based medicine

These studies have varying levels of evidence. Using the "pyramid of evidence" (Fig. 1.) Physician should always give preference to the results of the most demonstrative research. With regard to the effectiveness of therapy and prevention of these most conclusive studies are RCTs. In the case where there are many RCTs, systematic reviews can take into account the differences between them and learn a generalized estimate, based on the totality of RCTs. Therefore assumed that the findings of systematic reviews more evidence than the results of individual trials.

Studies are classified according to evidence at level 4 (Table 1). From which the highest is I.

Table 1. Levels of study evidences


Type of study


Metaanalysis RCT or at the least one well quality RCT



At least one well-organized controlled study without randomization or quasi-experimental studies (cohort)



Non experimental studies



Report of the expert committee or opinion and / or clinical experience of respected


Practical recommendations for diagnosis and treatment are based on data from all studies, not just the most demonstrative. This is especially important in situations where high quality data is not enough. For these purposes aggregate ranking of the available evidence. Recommendations are divided on the evidence at level 4, which is usually denoted by Latin letters - A, B, C, D.

Level A recommendations are based on research results that are attributable to the category I evidence and, therefore, have a high level of confidence. The reliability of the recommendations in the moderate level - in their formulation used materials research category II or III evidence. Level C recommendations are of limited reliability - (Category of evidence). Recommendation level D - rigorous scientific evidence available, are based on the expert committee reports or opinions and / or clinical experience of respected authorities

Table 2. Scale of evidences levels (modified scale SIGN)

Evidences levels

Evidences types



High-quality meta-analysis, systematic review or large RCTs with a very low probability of occurrence of systematic errors



High-quality meta-analysis, systematic review of RCTs, or RCTs with a low probability of occurrence of systematic errors.



Meta-analysis, systematic review of RCTs or RCTs with a high probability of bias.



High-quality systematic review of case-control studies or cohort studies. High-quality research case-control or cohort studies with a very low probability konfaundinga (vmeshivaniya factor) and a high probability of cause - effect relationship.


На латинице



High-quality research case-control or cohort studies with a low probability konfaundinga and with reasonable cause - effect relationship.



Study case-control or cohort studies likely to patronize konfaundinga without significant cause - effect relations.*



No analytical studies (clinical observation, description of clinical cases).



Experts' opinions, the consensus of experts.


* Studies with a level of evidence “-“ is not used as a basis for recommendations.

In training programs for clinical guidelines may apply its own, distinct from the reduced scale of levels of evidence recommendations. For example, the letter A denotes the presence of strong evidence of the usefulness of intervention, with - lack of evidence, E - strong evidence of risk (hazard) of intervention.

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