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Public Health 706: Perspectives on Community and Behavioral Health

Course and Library guide for locating resources for the Poster Project.

Levels of Evidence

Levels of evidence, shown in pyramid form.

  • Non-Evidence-based Expert Opinion - Commentary statements, speeches, or editorials written by prominent experts asserting ideas that are reached by conjecture, casual observation, emotion, religious belief, or ego. 
  • Non-EBP guidelines - practice guidelines that exist because of eminence, authority, eloquence, providence, or diffidence based approaches to healthcare.
  • News Articles - brief summaries of research or medical opinions written by journalists for the general public.
  • Editorials - Opinions asserted by experts, lay-people, non-experts, or anyone else in a news outlet, magazine, or academic journal.
  • Commentary - similar to an editorial, but it may be identified as a commentary, which can be an invited informal and non-reviewed short article pertaining to a particular concept or idea.

Let's Talk about Review Articles

Review articles are common in health literature. They are typically overviews of literature found on topics, but do not go so far as to meet the methodological requirements for a Systematic Review.

These articles may contain some critical analysis, but will not have the rigorous criteria that a Systematic Review does. They can be used to demonstrate evidence, albeit they do not make a very strong case as they are secondary articles and not originally conducted observational or experimental research.

  • Individual Case Reports - Scientific articles that describe a single instance of an occurrence, treatment, phenomenon, infection, disease, etc. Typically these are based upon patient records.
    • Example:  a patient enters the ER with some of the key symptoms for Mononucleosis, but complains of nausea and stomach pain. Upon further testing, the doctor concludes that the Mono infection has affected the liver. 

 

  • Case Series or Case Control Studies Articles outlining studies in which patients who already have a specific condition are compared with people who do not have the condition. The researcher looks back to identify factors or exposures that might be associated with the illness.  They often rely on medical records and patient recall for data collection.
    • Example:  A pediatrician notices that a children of a specific city jurisdiction are being diagnosed with lead poisoning. Upon further examination for the cause, she finds out that the city's dated and crumbling lead pipe plumbing infrastructure is affecting the water quality, leading to this high incidence.

 

  • Cohort StudiesArticles that identify a group of patients who are already taking a particular treatment or have an exposure, follow them forward over time, and then compare their outcomes with a similar group that has not been affected by the treatment or exposure being studied. Cohort studies are observational and not as reliable as randomized controlled studies, since the two groups may differ in ways other than in the variable under study
    • Example:  A group of doctors studied the long term health effects of people who smoked with particular frequencies alongside people who did not smoke at all. From this study doctors concluded that smoking poses significant health hazards such as increased risks of heart disease, cancers, and lung diseases.
  • Non-Randomized Control Trials - Articles that describe the background, methods, procedures, results, etc. around a new therapy, treatment, drug, etc. in a clinical environment with an experimental group and a control group--all knowing what type of intervention they are receiving.
    • Example:  Researchers investigating the difference between between yoga and acupuncture as relief for lower back pain. Since the activity involved in the trial cannot be disguised (as one might with a placebo), randomization cannot be a part of the research study. '

 

  • Randomized Control TrialsArticles that present carefully planned experiments that introduce a treatment or exposure to study its effect on real patients. They include methodologies that reduce the potential for bias (randomization and blinding) and that allow for comparison between intervention groups and control (no intervention) groups.  A randomized controlled trial is a planned experiment and can provide sound evidence of cause and effect. 
    • Example:  Researchers need to test the effects of a new drug for Parkinson's, so they recruit subjects for the study. A control group would be given the drugs standard for Parkinson's treatment, and the experimental group would have the trial drug. Participants would not know which treatment they receive during the trial.
  • Evidence-Based Medicine Practice Guidelines - Recommended devices, treatments, therapies, interventions, drugs, practices, protocols, etc. that are considered "best practices" which are supported by rigorous standards of evidence.
    • Example:  After thorough testing and experimentation, researchers, doctors, and product developers created and started using less-invasive oxygen monitoring devices to improve recovery times after surgeries. These are now standard equipment.

 

  • Systematic ReviewsArticles that focus on a clinical topic and answer a specific question. An extensive literature search is conducted to identify studies with sound methodology. The studies are reviewed, assessed for quality, and the results summarized according to the predetermined criteria of the review question. This is one of the most well-regarded types of Evidence-based Articles.
    • Example:  Researchers want to look at the literature on mammogram for breast cancer screenings to figure out--based on the literature--when someone should start getting regular mammograms as a preventive measure. They conduct a thorough literature search that consults multiple research databases and sources of literature, documenting every step, sorting through and selecting articles for inclusion in their research based on the criteria. They will then qualitatively analyze the results of selected articles to determine what type of recommendation for routine mammogram screening for breast cancer they should provide.

 

  • Meta-Analysis - Articles that thoroughly examine a number of valid studies on a topic and mathematically combine the results using accepted statistical methodology to report the results as if it were one large study.  This is often considered one of the highest levels of evidence-based research.

    Many Systematic Reviews Contain Meta-Analysis and will specify so, usually in the title.

    • ‚ÄčExample:  Researchers want to know what the rate of depression is in overweight women of Latin American heritage and examine self-reported sociocultural factors involved in their mental health. They conduct a literature search, exactly like researchers might do for a Systematic Review (see above) and do a quantitative analysis of the data using advanced statistical methods to synthesize conclusions from the numbers aggregated from a variety of studies.

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