Where Does Clinical Review Fall in Hierarchy of Evidence
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- EDUCATION & TRAINING (see Medical Teaching & Training)
- EPIDEMIOLOGY
- GENERAL MEDICINE (see Internal Medicine)
The showtime and earliest principle of evidence-based medicine indicated that a bureaucracy of evidence exists. Non all testify is the same. This principle became well known in the early 1990s as practising physicians learnt basic clinical epidemiology skills and started to appraise and apply show to their practice. Since evidence was described as a hierarchy, a compelling rationale for a pyramid was made. Evidence-based healthcare practitioners became familiar with this pyramid when reading the literature, applying evidence or teaching students.
Various versions of the evidence pyramid have been described, simply all of them focused on showing weaker study designs in the bottom (basic science and case series), followed by case–control and cohort studies in the middle, then randomised controlled trials (RCTs), and at the very pinnacle, systematic reviews and meta-assay. This clarification is intuitive and likely correct in many instances. The placement of systematic reviews at the height had undergone several alterations in interpretations, but was nonetheless idea of as an detail in a hierarchy.one Virtually versions of the pyramid clearly represented a hierarchy of internal validity (risk of bias). Some versions incorporated external validity (applicability) in the pyramid by either placing Due north-1 trials above RCTs (because their results are virtually applicable to private patients2) or by separating internal and external validity.three
Another version (the 6S pyramid) was also developed to describe the sources of evidence that tin exist used past show-based medicine (EBM) practitioners for answering foreground questions, showing a hierarchy ranging from studies, synopses, synthesis, synopses of synthesis, summaries and systems.4 This hierarchy may imply some sort of increasing validity and applicability although its main purpose is to emphasise that the lower sources of show in the hierarchy are least preferred in practise because they crave more expertise and fourth dimension to place, appraise and apply.
The traditional pyramid was deemed too simplistic at times, thus the importance of leaving room for argument and counterargument for the methodological merit of different designs has been emphasised.five Other barriers challenged the placement of systematic reviews and meta-analyses at the elevation of the pyramid. For instance, heterogeneity (clinical, methodological or statistical) is an inherent limitation of meta-analyses that can be minimised or explained but never eliminated.six The methodological intricacies and dilemmas of systematic reviews could potentially consequence in uncertainty and mistake.7 1 evaluation of 163 meta-analyses demonstrated that the estimation of treatment outcomes differed essentially depending on the analytical strategy beingness used.7 Therefore, we suggest, in this perspective, ii visual modifications to the pyramid to illustrate two contemporary methodological principles (figure 1). We provide the rationale and an example for each modification.
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Figure one
The proposed new evidence-based medicine pyramid. (A) The traditional pyramid. (B) Revising the pyramid: (one) lines separating the study designs become wavy (Grading of Recommendations Assessment, Development and Evaluation), (2) systematic reviews are 'chopped off' the pyramid. (C) The revised pyramid: systematic reviews are a lens through which evidence is viewed (applied).
Rationale for modification 1
In the early 2000s, the Grading of Recommendations Cess, Development and Evaluation (GRADE) Working Group developed a framework in which the certainty in prove was based on numerous factors and not solely on study design which challenges the pyramid concept.8 Study blueprint alone appears to be bereft on its own as a surrogate for risk of bias. Certain methodological limitations of a study, imprecision, inconsistency and indirectness, were factors independent from report design and tin can touch the quality of evidence derived from any study design. For example, a meta-assay of RCTs evaluating intensive glycaemic control in non-critically ill hospitalised patients showed a non-significant reduction in mortality (relative take a chance of 0.95 (95% CI 0.72 to ane.25)9). Resource allotment concealment and blinding were not adequate in nearly trials. The quality of this evidence is rated down due to the methodological imitations of the trials and imprecision (wide CI that includes substantial benefit and harm). Hence, despite the fact of having v RCTs, such evidence should not be rated high in any pyramid. The quality of evidence can also be rated up. For example, nosotros are quite certain almost the benefits of hip replacement in a patient with disabling hip osteoarthritis. Although not tested in RCTs, the quality of this testify is rated up despite the written report design (non-randomised observational studies).10
Therefore, the starting time modification to the pyramid is to change the straight lines separating study designs in the pyramid to wavy lines (going up and down to reflect the GRADE approach of rating up and downwardly based on the various domains of the quality of evidence).
Rationale for modification 2
Another challenge to the notion of having systematic reviews on the acme of the evidence pyramid relates to the framework presented in the Journal of the American Medical Association User'south Guide on systematic reviews and meta-assay. The Guide presented a ii-pace approach in which the brownie of the process of a systematic review is evaluated start (comprehensive literature search, rigorous written report pick procedure, etc). If the systematic review was deemed sufficiently apparent, so a 2d step takes place in which nosotros evaluate the certainty in evidence based on the GRADE approach.11 In other words, a meta-analysis of well-conducted RCTs at low gamble of bias cannot exist equated with a meta-assay of observational studies at higher take a chance of bias. For example, a meta-assay of 112 surgical example series showed that in patients with thoracic aortic transection, the bloodshed rate was significantly lower in patients who underwent endovascular repair, followed by open repair and not-operative direction (9%, xix% and 46%, respectively, p<0.01). Conspicuously, this meta-analysis should not be on meridian of the pyramid similar to a meta-analysis of RCTs. Subsequently all, the bear witness remains consistent of non-randomised studies and probable subject to numerous confounders.
Therefore, the second modification to the pyramid is to remove systematic reviews from the top of the pyramid and apply them as a lens through which other types of studies should exist seen (ie, appraised and applied). The systematic review (the process of selecting the studies) and meta-analysis (the statistical aggregation that produces a single upshot size) are tools to consume and use the evidence past stakeholders.
Implications and limitations
Changing how systematic reviews and meta-analyses are perceived by stakeholders (patients, clinicians and stakeholders) has important implications. For example, the American Centre Association considers bear witness derived from meta-analyses to have a level 'A' (ie, warrants the about confidence). Re-evaluation of testify using Grade shows that level 'A' evidence could have been high, moderate, low or of very low quality.12 The quality of evidence drives the force of recommendation, which is one of the final translational steps of research, most proximal to patient care.
1 of the limitations of all 'pyramids' and depictions of bear witness hierarchy relates to the underpinning of such schemas. The construct of internal validity may have varying definitions, or be understood differently among bear witness consumers. A limitation of considering systematic review and meta-analyses as tools to consume show may undermine their role in new discovery (eg, identifying a new side upshot that was not demonstrated in individual studies13).
This pyramid can be also used equally a teaching tool. EBM teachers can compare information technology to the existing pyramids to explain how certainty in the testify (too called quality of evidence) is evaluated. It tin be used to teach how bear witness-based practitioners can appraise and apply systematic reviews in practice, and to demonstrate the evolution in EBM thinking and the modern agreement of certainty in evidence.
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