Evidence-Based Medicine
Below is the evidence based medicine pyramid, which highlights different types of clinical studies, and the level of information that they contain.
In evidence-based medicine, decisions about treatments are determined by scientific research.
"Evidence based medicine is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients." Dr. David L. Sakett, Evidence Based Practice: what it is and what it isn't, 1996.
Evaluating scientific research to determine the best course of action is time-consuming and involved:
- First, there need to be studies on both the problem at hand and the proposed intervention.
- Next, these studies need to be rigorous and as free from bias as possible.
- Finally, these studies need to point to a single conclusion or intervention.
However, there are issues to look out for:
- Not every problem and intervention has been published because not every type of intervention will be funded for research, and new interventions are being developed and then tested in clinical trials all of the time.
- Sometimes studies are not as rigorous or bias-free as scientist design them, and publication bias, which can favor studies with positive results, impacts the research we have access to.
- Rarely do all the studies agree on the results; but the more studies that do agree, the more reliable that conclusion.
- Systematic reviews and meta-analyses are at the top of the evidence pyramid because they provide information that is filters through more researchers. However, not all studies included in a systematic review will be well conducted, and not all systematic reviews are well conducted themselves. Therefore, you cannot trust information simply because it is coming from a meta-analysis or a systematic review. Evaluation is critical.
Types of studies in this portion of the guide include
Individual case studies: These types of studies often describe a medical anomaly and spark the idea of a solution or treatment that is applicable to a broader population.
Clinical trials: new interventions are tested and reported.
Systematic reviews: the results from multiple trials are synthesized, studied, and evaluated.
Check out the TED talk below by Dr. Ben Goldacre to learn more about the dangers of publication bias:
Medical Statistics
Sometimes called a systematic "study of studies," a systematic review documents the results from multiple trials. The systematic review is defined by its comprehensive search approach in which researchers work to find all documented studies on a given research question. The results from searches are synthesized, studied, and evaluated in a transparent and heavily documented collaborative process. This is why a well conducted systematic review is one of the most useful types of research you can find.
Cochrane libraryProvides full-text access to Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, and Cochrane Clinical Answers. "Cochrane reviews are systematic summaries of evidence of the effects of healthcare interventions. They are intended to help people make practical decisions." (The Cochrane Collaboration, 2019)
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Embase This link opens in a new window
Provides bibliographical information for scholarly material in biomedical and pharmacological sciences.
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PubMed This link opens in a new window
Indexes journal articles in life sciences with a concentration on biomedicine. Contains material not yet indexed in Medline.
Uses Medical Subject Headings (MeSH) indexing with tree, tree hierarchy, subheadings and explosion capabilities.
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Case studies focus on in-depth documentation of one particular medical case that occurred in a real life context. They are useful when there is a need to explore an in-depth understanding of a particular issue or phenomenon of interest, particularly when an issue is not yet well understood.
- AccessMedicine Case Files Collection This link opens in a new window
Provides up-to-date and interactive content for basic science, clinical medicine, and post-graduate level cases for learning through exposure to realistic patient cases.
- New England Journal of Medicine Clinical CasesRead recently published clinical cases by the New England Journal of Medicine
- BMJ Case IndexSearch Case Reports by specialty (Anesthesia, Dentistry, Family Medicine, Emergency Medicine, Neurology, OB, Pediatric, Etc.) You can also search by publication dates and altmetrics, and find latest articles).
- Case of the MonthCase Reports available through the University of Pittsburgh Department of Pathology. Search for the case of the month or if you scroll down the page, there is a tab called Case Studies click on that. Here you can do a keyword search, a case index by patient history, date or patient diagnosis.
- A to Z case listsNortheast Ohio Medical University cast list of free resources
"Clinical trials are clinical research studies involving human participants assigned to an intervention in which the study is designed to evaluate the effect(s) of the intervention on the participant and the effect being evaluated is a health-related biomedical or behavioral outcome." (NIH, Office of Intramural Research, FAQ page) Clinical trials are useful when researching new interventions that have not yet been heavily documented.
- Clinicaltrials.govClinicalTrials.gov is a Web-based resource that provides patients, their family members, health care professionals, researchers, and the public with easy access to information on publicly and privately supported clinical studies on a wide range of diseases and conditions.
- ISRCTNThe ISRCTN registry is a primary clinical trial registry recognised by WHO and ICMJE that accepts all clinical research studies (whether proposed, ongoing or completed), providing content validation and curation and the unique identification number necessary for publication. All study records in the database are freely accessible and searchable.
- WHO ICTRPThe Clinical Trials Search Portal provides access to a central database containing the trial registration data sets provided by the registries listed on the right. It also provides links to the full original records.
- Center WatchProvides information on clinical trials and drugs in trials that have not yet been approved.
Evaluation is key
While systematic reviews synthesize multiple studies, and meta-analyses provide statistical measures that summarize the data from these studies, not all systematic reviews are conducted well. This is why evaluation is key.
In order to assess the article for risk of bias, which is essential for critically appraising the evidence, we can move through the FRISBEE criteria:
F: Follow-up (Dropouts or those lost to follow-up create missing data that disrupt the balance in groups created by randomization—this can obscure results)
R: Randomization and concealed allocation (Randomization guarantees that each subject has the same chance of entering any group.)
I: Intention-to-treat (ITT preserves the balance of prognostic factors in groups created by the original random allocation. It avoids overly optimistic estimates of treatment efficacy resulting from excluding non-compliers)
S: Similar baseline characteristics (Similar baseline characteristics help to ensure that there are similar confounding variables, which helps to keep the study outcome balanced)
B: Blinding (Blinding equalized the effect of patient and therapist expectations on outcome)
E: Equal treatment (Equal treatment helps guarantee that the groups will remain prognostically balanced by avoiding systematic differences in care that could skew the results.)
E: Equivalence to your patient/population (How applicable is this study to the population that you are studying?)
