Evidence-based medicine

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Dr. Ahmed Mostafa

Assist. Prof. of anesthesia & I.C.U.

Evidence-based medicine

Definition

 It is the conscientious, explicit and judicious use ofcurrent best evidence in making decisions about thecare of individual patients.

It seeks to assess the strength of the evidence of risksand benefits of treatments and diagnostic tests.

This helps clinicians predict whether a treatment willdo more good than harm.

Benefits

 It offers the surest and most objective way todetermine and maintain consistently highquality and safety standards in medicalpractice.

 It can help speed up the process oftransferring clinical research findings intopractice.

 It has the potential to reduce health-care costssignificantly.

Quality of clinical trials

Evidence-based medicine attempts to objectivelyevaluate the quality of clinical research bycritically assessing techniques reported byresearchers in their publications.

•Trial design considerations.

•Generalizability considerations.

•Follow-up.

•Statistical power.

Evidence is obtained from valid scientific research. To obtainevidence on a clinical situation, the following steps should betaken:

Clinical question. the patients, intervention in question,comparison group and outcome required from thisintervention.

Relevance: Is the problem common, will my patients careabout it and will I really change my practice based on thisevidence?

Validity: Is there an error in the methods, e.g., bias, orconfounding 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 andsystematic reviews of triple-blind randomizedplacebo-controlled clinical trials withconcealment 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 suitablestudies on a subject, review the quality of the studies, andcombine results that are of the best quality available. Ifspecific 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 availableevidence is inconclusive. Thus, they should be considered guides todecision making in the face of uncertainty, and their conclusions shouldbe interpreted with caution.

b- Mega trials are usually multicenter, and sometimes multinational, tomaximize recruitment and enable early conclusion. This provides abroad range of settings and offers an opportunity to identify otherpatient, 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 chosengroups with similar characteristics. One group receives the intervention(drug, educational program, etc.) being studied and the other receives aplacebo or whatever the routine treatment is. Outcomes are evaluated tosee which treatment is better. Ideally, neither the person recording theoutcomes nor the subject knows in which group the subject belongs(this is called double blinding). The RCT is the “gold standard” forassessing 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 inquestion. It is preferable that the investigator performing the test inquestion is not shown the results of other investigations. The analysisshould provide estimates of, at least, the sensitivity (true positive/ [truepositive + false negative]), specificity (true negative/ [true negative +false positive]) and positive predictive value (true positive/ [truepositive+ false positive]).

Types of studies

4- Cohort (longitudinal) study:

A group of people is observed over time to see if theircharacteristics are associated with the development ofcertain outcomes. In a review, several cohort studies onthe same subject are evaluated for their quality, results arepooled and a general recommendation is made. The cohortstudy is the study of choice to assess harm, prognosisand 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 intheir pasts to see if certain risk factors were present.A review compiles the results of several studies andmakes conclusions. Case-control study is suitable toassess risk (etiology) if the cohort study will not bepractical.

Types of studies

6- Cross-sectional (prevalence) study (surveys):A sample from a larger population is studied for prevalence orexposures and outcomes of interest at the same time. There is nocomparison group.

7- Case series:

All the patients with a specific problem are described. There is nocomparison group.

8- Expert opinion:

A person gives her/his opinion for practice, without havingevidence to support it.