Thread by @dnunan79

Very comprehensive evaluation of GRADE its preferred use as method for ‘determining causative causal associations between nutrients or other food substances (NOFSs) and chronic diseases’

Some key bits that put red meat reviews in context:

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https://twitter.com/kcklatt/status/1180238670789562369

“After reviewing the systems....& based on the knowledge & experience of committee members about what would meet the needs of DRI committees..., the committee adopted the GRADE system as the reference point for the evidence reviews relating to NOFS-chronic disease considerations”

‘GRADE has been applied to nutrition-related systematic reviews (Garcia-Larsen et al. 2016; Mayhew et al. 2016; Naude et al. 2014; Pennant et al. 2015; Santesso et al., 2012) and is the method generally used by WHO to support guideline development, including for nutrition topics’

‘......GRADE has identified five paradigmatic situations in which strong recommendations are warranted in the face of low certainty evidence (Andrews et al., 2013b).’

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‘Dealing with Multiple Comparators:’

‘one could ask “what is the effect of replacing SFA w monounsaturated FAs or various types of polyunsaturated fatty acids on cardiovascular disease outcomes” but extract data to support examination of each type of replacement separately.’
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‘However, when multiple alternatives exist, it is unlikely that the primary literature will have compared each alternative to every other alternative. In this case, inferences regarding the relative merits of the alternatives require indirect comparisons.’
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‘A novel statistical methodology for simultaneously considering all direct and indirect comparisons, network meta-analysis, is now available for dealing w such situations.
GRADE has developed guidance for rating certainty of evidence in the context of network meta-analysis’
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‘As discussed above, RCTs, as true experiments, provide the best overall evidence of causation, but the actual certainty in the evidence depends on the certainty of those trials.’
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‘Other criteria and systems for approaching causation exist, such as the Bradford Hill criteria (Hill, 1965). Parascandola and Weed reviewed the epidemiological literature on causation and found multiple definitions (Parascandola and Weed, 2001).’
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‘After considering these approaches in detail and based on the committee’s evaluation of the GRADE approach, the recommendation is that to accept the likelihood of a causal relationship. between an NOFS and a chronic disease outcome,...
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‘a moderate rating of the relevant overall evidence base derived using GRADE criteria is needed. Lesser levels of confidence in causation should not lead to actionable recommendations or, in the case here, the development of chronic disease DRIs.’
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‘Presumably, to move forward with developing chronic disease DRIs, determination of an intake-response in data from observational studies as part of the evidence rating also would be needed.’
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‘The GRADE system does not specify either a minimum number of studies or participants.... or the characteristics of the study design (e.g., observational studies have established the causal relationship of smoking and lung cancer)’
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