By Dr. Ahmed Mostafa Assist. Prof. of anesthesia & I.C.U. Evidence-based medicine

Definition  It is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients.  It seeks to assess the strength of the evidence of risks and benefits of treatments and diagnostic tests.  This helps clinicians predict whether a treatment will do more good than harm.

Benefits  It offers the surest and most objective way to determine and maintain consistently high quality and safety standards in medical practice.  It can help speed up the process of transferring clinical research findings into practice.  It has the potential to reduce health-care costs significantly.

Quality of clinical trials Evidence-based medicine attempts to objectively evaluate the quality of clinical research by critically assessing techniques reported by researchers in their publications. Trial design considerations. Generalizability considerations. Follow-up. Statistical power.

Evidence is obtained from valid scientific research. To obtain evidence on a clinical situation, the following steps should be taken:  Clinical question. the patients, intervention in question, comparison group and outcome required from this intervention.  Relevance: Is the problem common, will my patients care about it and will I really change my practice based on this evidence?  Validity: Is there an error in the methods, e.g., bias, or confounding and was power of the study addressed?  Applicability: Is the information useful to your patients?

Evidence quality can be assessed based on: The source type (from meta-analyses and systematic reviews of triple-blind randomized placebo-controlled clinical trials with concealment of allocation). Statistical validity. Clinical relevance. Currency. Peer-review acceptance.

Types of studies 1- Systematic review (meta-analysis - mega trials): In a systematic review, reviewers search for all suitable studies on a subject, review the quality of the studies, and combine results that are of the best quality available. If specific statistical techniques were used to give a pooled (combined) result, this is called meta-analysis.

Types of studies a- Meta-analyses are systematic reviews performed when available evidence is inconclusive. Thus, they should be considered guides to decision making in the face of uncertainty, and their conclusions should be interpreted with caution. b- Mega trials are usually multicenter, and sometimes multinational, to maximize recruitment and enable early conclusion. This provides a broad range of settings and offers an opportunity to identify other patient, clinician, and institutional factors that may influence outcome. Mega trials are therefore less biased and are more reliable.

Types of studies 2- Randomized controlled trial: A randomized controlled trial (RCT) compares two randomly chosen groups with similar characteristics. One group receives the intervention (drug, educational program, etc.) being studied and the other receives a placebo or whatever the routine treatment is. Outcomes are evaluated to see which treatment is better. Ideally, neither the person recording the outcomes nor the subject knows in which group the subject belongs (this is called double blinding). The RCT is the “gold standard” for assessing treatment and preventive interventions.

Types of studies 3- Diagnostic study: An ideal diagnostic test study should be prospective or cross-sectional. It should compare the performance of the test to a “gold standard” test, which is the current best method for diagnosing the condition in question. It is preferable that the investigator performing the test in question is not shown the results of other investigations. The analysis should provide estimates of, at least, the sensitivity (true positive/ [true positive + false negative]), specificity (true negative/ [true negative + false positive]) and positive predictive value (true positive/ [true positive+ false positive]).

Types of studies 4- Cohort (longitudinal) study: A group of people is observed over time to see if their characteristics are associated with the development of certain outcomes. In a review, several cohort studies on the same subject are evaluated for their quality, results are pooled and a general recommendation is made. The cohort study is the study of choice to assess harm, prognosis and etiology.

Types of studies 5- Case-control study: A case-control study compares two similar groups, one with and one without a disease, and looks in their pasts to see if certain risk factors were present. A review compiles the results of several studies and makes conclusions. Case-control study is suitable to assess risk (etiology) if the cohort study will not be practical.

Types of studies 6- Cross-sectional (prevalence) study (surveys): A sample from a larger population is studied for prevalence or exposures and outcomes of interest at the same time. There is no comparison group. 7- Case series: All the patients with a specific problem are described. There is no comparison group. 8- Expert opinion: A person gives her/his opinion for practice, without having evidence to support it.

Grades of Recommendations Grade of recommendationLevel of evidenceInterventions A 1a Systematic review of randomized controlled trials 1bIndividual randomized controlled trial B 2aSystematic review of cohort studies 2bIndividual cohort study 3aSystematic review of case-control studies 3bIndividual case-control study C4Case series R5 Expert opinion without explicit critical appraisal or based on physiology or bench research

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Thank you Dr. Ahmed Mostafa