Use and Applications of Systematic Reviews in Public Health Nutrition
ABSTRACT Decisions related to a spectrum of nutrition-related public health and clinical concerns must consider many factors and are best informed by evaluating the totality and quality of the evidence. Systematic review (SR) is a structured process to evaluate, compare, and synthesize relevant evidence for the SR-specific question(s). Applications of SR are exemplified here through the discussion of four case studies: research agenda, nutrient reference intakes, dietary guidance, and practice guidelines. Concerns that SR cannot be effectively applied to nutrition evidence because of the lack of an unexposed comparator and the complex homeostasis in nutrition are discussed. Central to understanding the applicability of SR is its flexibility in defining key inclusion criteria and rigorous elements as appropriate for the SR-specific question(s). Through the reduction of bias and random error by explicit, reproducible, comprehensive, and rigorous examination of all of the evidence, SR informs the scientific judgment needed for sound evidence-based public health nutrition. Expected final online publication date for the Annual Review of Nutrition Volume 34 is July 17, 2014. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
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ABSTRACT: Recent Institute of Medicine (IOM) reviews of the process for deriving Dietary Reference Intakes (DRIs) suggest that determining the need for a new nutrient review should be evaluated against criteria set a priori. After selecting the criterion of significant new and relevant research, a working group of US and Canadian government scientists used results from a systematic review and 2 conferences on vitamin D and health to evaluate whether significant new and relevant scientific evidence had become available since the 1997 IOM publication of the DRIs for vitamin D. This working group concluded that there appears to be new research meeting the criteria for 4 key DRI questions. The new research is of larger quantity and quality for the elderly than for other groups, but overall 1) adds to the bone-related and status evidence available to the 1997 DRI Committee for several of the life-stage groups, 2) identifies new outcomes with respect to risk of falls and performance measures in the elderly and potential adverse effects, and 3) provides additional information on dose-response relations between intakes and circulating 25-hydroxyvitamin D concentrations and between 25-hydroxyvitamin D concentrations and several health outcomes (ie, bone-related outcomes for all ages and risk of falls and performance measures in older adults). Members of the working group concluded that significant new and relevant research was available for reviewing the existing DRIs for vitamin D while leaving the decision of whether the new research will result in changes to the current DRIs to a future IOM-convened DRI committee.American Journal of Clinical Nutrition 01/2009; 89(3). DOI:10.3945/ajcn.2008.26903 · 6.92 Impact Factor
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ABSTRACT: Although there is increasing interest in the evaluation of complex interventions, there is little guidance on how evidence from complex interventions may be reviewed and synthesized, and the relevance of the plethora of evidence synthesis methods to complexity is unclear. This article aims to explore how different meta-analytical approaches can be used to examine aspects of complexity; describe the contribution of various narrative, tabular, and graphical approaches to synthesis; and give an overview of the potential choice of selected qualitative and mixed-method evidence synthesis approaches. The methodological discussions presented here build on a 2-day workshop held in Montebello, Canada, in January 2012, involving methodological experts from the Campbell and Cochrane Collaborations and from other international review centers (Anderson L, Petticrew M, Chandler J, et al. Introduction: systematic reviews of complex interventions. In press). These systematic review methodologists discussed the broad range of existing methods and considered the relevance of these methods to reviews of complex interventions. The evidence from primary studies of complex interventions may be qualitative or quantitative. There is a wide range of methodological options for reviewing and presenting this evidence. Specific contributions of statistical approaches include the use of meta-analysis, meta-regression, and Bayesian methods, whereas narrative summary approaches provide valuable precursors or alternatives to these. Qualitative and mixed-method approaches include thematic synthesis, framework synthesis, and realist synthesis. A suitable combination of these approaches allows synthesis of evidence for understanding complex interventions. Reviewers need to consider which aspects of complex interventions should be a focus of their review and what types of quantitative and/or qualitative studies they will be including, and this will inform their choice of review methods. These may range from standard meta-analysis through to more complex mixed-method synthesis and synthesis approaches that incorporate theory and/or user's perspectives.Journal of clinical epidemiology 08/2013; 66(11). DOI:10.1016/j.jclinepi.2013.06.005 · 5.48 Impact Factor
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ABSTRACT: Current medical training often does not include the formal study of trial design, forcing clinicians to acquire this knowledge independently. This article reviews the foundational elements of clinical trial design. An overarching hierarchy of clinical evidence is introduced, and the relative strengths and limitations of the major types of study designs are discussed. A corollary to the hierarchy of evidence in trial designs is proposed for trial outcomes: the "pyramid of endpoints." This pyramid represents a spectrum of outcomes from tangible health events to intermediate markers with no direct physical impact on an individual. The potential advantages and difficulties inherent in the use of surrogate endpoints for final health outcomes are explored. Randomized controlled trials utilizing "hard" clinical endpoints are advocated as the most efficient and reliable way to directly assess the benefits and harms of a therapy; however, using a case study of treatments for hepatocellular carcinoma, we highlight the challenges that can complicate even the highest levels of evidence. All trials have a "signal-to-noise" ratio - this review emphasizes the need for careful and deliberate consideration of the potential limitations of every study, and provides basic tools to assist the practitioner in identifying common pitfalls of clinical trials.Journal of Hepatology 03/2009; 50(4):817-26. DOI:10.1016/j.jhep.2009.01.005 · 10.40 Impact Factor