Evidence-based medicine (EBM) is defined as, "the conscientious, explicit,
and judicious use of current best evidence in making decisions about the care
of individual patients.(Sackett, DL, et. al.)
Levels of Evidence
Figure adapted from Greenhalgh T. How to Read a Paper:
The Basics of Evidence-Based Medicine. Hoboken: John Wiley & Sons, Incorporated; 2010.
Figure 2.1 A simple hierarchy of evidence for assessing the quality of trial design in therapy studies.
This Figure and guide is based upon the libguide developed by Levy Library at
Icahn School of Medicine at Mount Sinai.
A clinical question takes the form of a PICO query.
Patient / Problem
Intervention
Comparison
Outcome
You will develop your PICO in a way that can be entered as an advanced search using boolean operators and limiting facets within a given database.
A systematic review is "a review that uses explicit, systematic methods to collate and synthesise findings of studies that address a clearly formulated question".1
Systematic reviews are useful for:
Meta-analyses, while often part of systematic reviews, are not interchangeable with them. They use statistical analysis to combine data from the studies found in the systematic review process. These studies must be homogenous enough that the data from them can be pooled together.
Limitations of systematic reviews include:
Sources:
Finding evidence to answer clinical questions can be challenging for several reasons, chief among them is the gut of available information. The PubMed database contains over 33 million citations, with over 800,000 citations being added annually. These citations include letters, commentaries, narrative reviews, errata and other types of information that are not appropriate for use in clinical decision making.
Next, the enormous variation in human language can make searching challenging. Consider the number of results in PubMed for a variety of search terms one might reasonably use to search for evidence on whether it is safe and effective to treat a pulmonary embolism patient as an outpatient.
| Search Terms | # of Results |
|---|---|
| pulmonary embolism oral anticoagulants outpatient | 180 |
| pulmonary embolism outpatient | 1,314 |
| pulmonary embolism outpatient treatment | 803 |
| pulmonary embolism treatment setting | 2,037 |
In addition, though the evidence hierarchy is straightforward, the best available evidence may not come from the optimal study type. For example, if treatment effects found in well designed cohort studies are sufficiently large and consistent, those cohort studies may provide more compelling evidence than the findings from a weaker RCT. And, of course, the strongest research evidence does not exist for every question (e.g. it is difficult to blind studies of surgical treatments and ethical standards prohibit RCTs that would expose subjects to harm).
Because searching the primary literature is challenging and time consuming, a number of resources exist to help clinicians identify the most relevant evidence to answer their clinical questions. These include clinical practice guidelines from professional organizations and commercial resources which aim to collect and synthesize all available literature on a topic (referred to in this guide as evidence summary resources).
*(Source: Levy Library, Icahn School of Medicine)
In the critical appraisal process, you are seeking to determine what accounts for a study's results. Specifically, you are looking to determine whether a study's results are most likely due to bias, chance, confounding, or truth.1
The questions needed to critically appraise a specific study will depend on the study design but broadly speaking, when appraising a study, you are looking to determine:
The ability to critically appraisal a study requires an understanding of epidemiological and biostatistical concepts, particularly clinical study design, biases and confounders in clinical research, basic biostatistics, and common measures of association in biomedical studies.
1. Fletcher GS, Fletcher RH. Clinical epidemiology : the essentials . 6th ed. Philadelphia: Lippincott Williams & Wilkins/Wolters Kluwer; 2021. Chapter 12, Cause; p.204-218
One of the 3 key principles of evidence-based medicine (EBM) is that the evidence alone is never sufficient to make a clinical decision. Clinicians require expertise in interpreting the patient dilemma (in its clinical, social, and economic contexts) and in identifying the body of evidence that bears on optimal patient treatment. These considerations, however, are not enough. Evidence-based medicine requires that clinical decisions be consistent with the informed values and preferences of the patient.1
Eliciting a patient's values and preferences and taking them into account when making decisions is a complex skill set. Below we suggest readings and resources to help help clinicians engage in this process.
This is an AMA writing guide that has been developed by the Jerry Falwell Library.
The e-book of the AMA Style Manual 11th edition can be found here.
This an APA writing guide that has been developed by the Jerry Falwell Library