
Evidence-based medicine
Evidence—based medicine is an approach to medical practice in which decisions on the use of preventive, diagnostic and therapeutic measures are made based on available evidence of their effectiveness and safety, and such evidence is searched, compared, generalized and widely disseminated for use in the interests of patients. This definition of evidence-based medicine was proposed in 1993 by the Evidence Based Medicine Working Group.
An example of an evidence-based medicine tool is preclinical and clinical studies, the results of which are evidence of the safety and effectiveness of a particular drug.
The reliability and informativeness of the results obtained in the course of clinical trials can be judged by the levels and values of reliability and evidence of the data obtained in evidence-based medicine.
The value of evidence
Class I - evidence and/or expert agreement that therapeutic or diagnostic intervention is useful and effective.
Class II - conflicting data and/or divergent expert opinions on the benefits/effectiveness of treatment or diagnostic measures.
IIa - the significance of evidence/opinions is rather in favor of intervention.
IIb - the benefit or effect is less convincing.
Class III - evidence and/or expert agreement that therapeutic or diagnostic intervention is ineffective and may be dangerous.
Evidence levels
A - at least two randomized trials* supporting the recommendations.
B - one randomized trial and/or meta-analysis of non-randomized trials** supporting the recommendations.
C - consensus of expert opinion.
*Randomized trials are studies in which the distribution of the studied drug among groups of patients is carried out randomly.
**Meta–analysis of research - combining the results of several studies using statistical methods to test one or more interrelated scientific hypotheses.