Thread by @just1doctorwala

Let's talk about "evidence" in Evidence Based Medicine
#MedTwitter
We have Levels of evidence
Sources regarded as strong evidence include clinical practice guidelines, systematic reviews with meta-analyses, systematic reviews alone, individual randomized controlled trials (RCT)

and well-designed non-randomized control studies. The hierarchy of evidence for treatment questions is based on the notion of causation and the need to control bias.

see figure below

Although each level may contribute to the total body of knowledge, "...not all levels are equally useful for making patient care decisions."

As you progress up the pyramid, the number of studies and correspondingly, the amount of available literature decreases, while at the same time their relevance to answering clinical questions increases

see figure below

Knowing which segment of the literature is appropriate for clinical decision-making and how to quickly retrieve this information is important to evidence-based practice.

For example, the study methodology and level of evidence will differ based on the type of question asked, such as those derived from issues of therapy/prevention, diagnosis, etiology, and prognosis.

The Table below reviews the type of question and the highest levels of evidence based on the study methodology.

For example, for questions associated with therapy and prevention, the highest level of evidence will be from meta-analyses or systematic reviews of randomized controlled trials (RCTs), since the objective of these studies is to test interventions demonstrating cause and effect

and to select treatments that improve the condition/disease and avoid adverse events.

Correctly identifying the type of study to answer the question is an important skill to develop to access the appropriate evidence when searching the healthcare literature.

Correctly identifying the type of study to answer the question is an important skill to develop to access the appropriate evidence when searching the healthcare literature.

Ideally, a meta-analysis or systematic review of RCTs would be available on the treatment being considered. If one were not available, then the next best evidence would be from a well-conducted individual RCT.

However, when the focus of the question is on long-term outcomes of treatment, then it is a question of prognosis where the highest level of evidence would be provided by a systematic review of inception cohort studies, which are studies that follows patients from when a disease

or condition first manifests itself clinically. And again, if a meta-analysis or systematic review were not available, the next highest level would be an individual inception cohort study, and so on down the hierarchy as shown in the table above

Two important concepts to keep in mind are that:
1) for any type of question, having a well-conducted meta-analysis or systematic review typically provides stronger evidence than a single study,

and

2) a meta-analysis or systematic review is only as good as the individual studies that comprise it.

all of the above from

dentalcare.com/en-us/professi…

This is how evidence based medicine works
this is SCIENCE