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Rating System For The Hierarchy Of Evidence Melnyk REPACK

Rating System For The Hierarchy Of Evidence Melnyk >

Rating System For The Hierarchy Of Evidence Melnyk REPACK

Melnyk, B.M. & Fineout-Overholt, E. (2015). "Box 1.3: Rating system for the hierarchy of evidence for intervention/treatment questions" in Evidence-based practice in nursing & healthcare: A guide to best practice (3rd ed.) (pp. 11). Philadelphia, PA: Wolters Kluwer Health.

About Levels of Evidence and the Hierarchy of Evidence: While Levels of Evidence correlate roughly with the hierarchy of evidence (discussed elsewhere on this page), levels of evidence don't always match the categories from the Hierarchy of Evidence, reflecting the fact that study design alone doesn't guarantee good evidence. For example, the systematic review or meta-analysis of randomized controlled trials (RCTs) are at the top of the evidence pyramid and are typically assigned the highest level of evidence, due to the fact that the study design reduces the probability of bias (Melnyk, 2011), whereas the weakest level of evidence is the opinion from authorities and/or reports of expert committees. However, a systematic review may report very weak evidence for a particular practice and therefore the level of evidence behind a recommendation may be lower than the position of the study type on the Pyramid/Hierarchy of Evidence.

The pyramid below represents the hierarchy of evidence, which illustrates the strength of study types; the higher the study type on the pyramid, the more likely it is that the research is valid. The pyramid is meant to assist researchers in prioritizing studies they have located to answer a clinical or practice question.

Qualitative studies are not included in the Hierarchy of Evidence above. Since qualitative studies provide valuable evidence about patients' experiences and values, qualitative studies are important--even critically necessary--for Evidence-Based Nursing. Just like quantitative studies, qualitative studies are not all created equal. The pyramid below shows a hierarchy of evidence for qualitative studies.

In contrast to the case-control and slightly higher on the levels of evidence hierarchy,3 the cohort study is usually done in a prospective fashion (although it can be done retrospectively) and usually follows two groups of patients. One of these groups has a risk factor or prognostic factor of interest and the other does not. The groups are followed to see what the rate of development of a disease or specific outcome is in those with the risk factor as compared to those without. Given that this is usually done prospectively it falls higher within the hierarchy as data collection and follow-up can be more closely monitored and attempts can be made to make them as complete and accurate as possible. This type of study design can be very powerful in some instances. For example, if one wanted to see what the effect of smoking was on nonunion rates, it wouldn't be ethical or generally possible to randomize patients with fractures into those who are going to smoke and those who are not. However, by following two groups of patients, smokers and non-smokers with tibial fractures for instance, one can then document nonunion rates between the two groups. In this case, because of its prospective design, groups can at least be matched to try and limit the bias of at least those prognostic variables that are known, such as age, fracture pattern or treatment type to name a few.

"Figure 2.2 [in context of book] shows our eight-level evidence hierarchy for Therapy/intervention questions. This hierarchy ranks sources of evidence with respect the readiness of an intervention to be put to use in practice" (Polit & Beck, 2021, p. 28). Levels are ranked on risk of bias - level one being the least bias, level eight being the most biased. There are several types of levels of evidence scales designed for answering different questions. "An evidence hierarchy for Prognosis questions, for example, is different from the hierarchy for Therapy questions" (p. 29).

Regarding the impor


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