Guidelines Dietary - Eat For Health

The evidence was assessed according to NHMRC levels and grades for recommendations for developers ofguidelines, 42 which allowed each article to be critically appraised and assigned a level of evidence based on ahierarchy according to the type of research question. As this review looked at causality and intervention researchquestions the following hierarchy was used.Table B3: Levels of evidence in the literature reviewLevel ILevel IILevel III-1Level III-2Level III-3Level IVA systematic review of level II studiesA randomised controlled trialA pseudorandomised controlled trialA comparative study with concurrent controls:• Non-randomised experimental trial• Cohort study• Case-control study• Interrupted time series with a control groupA comparative study without concurrent controls:• Historical control study• Two or more single arm study• Interrupted time series without a parallel control groupCase series with either post-test or pre-test/post-test outcomesData was extracted from included studies and assessed for strength of evidence, size of effect and relevance ofevidence according to standardised NHMRC processes. 32,40-42 The components of the body of evidence; evidencebase (quantity, level and quality of evidence); consistency of the study results; clinical impact; generalisability; andapplicability to the Australian context) – were rated as excellent, good, satisfactory or poor according to standardNHMRC protocols. 38,42 The reviewers then translated the evidence into a draft body of evidence statement. The draftevidence statements were graded A to D according to standard NHMRC protocols: 42• Grade A indicates that the body of evidence can be trusted to guide practice• Grade B indicates that the body of evidence can be trusted to guide practice in most situations• Grade C indicates that the body of evidence provides some support for the recommendations but care shouldbe taken in its application• Grade D indicates that the body of evidence is weak and any recommendation must be applied with caution.In order to reduce potential risks associated with advice being based on findings of single or only a few studies,the Working Committee and DAA contractors advised that a minimum of five quality studies were required beforea graded draft evidence statement could be made. The individual studies included in meta-analysis studies wereconsidered as separate studies.Once the evidence statements had been drafted and graded, the NHMRC commissioned a methodologistthrough the NHMRC methodologist panel, Ms Philippa Middleton from the University of Adelaide, to assist theWorking Committee to ensure that the review activities had been undertaken in a transparent, accurate andunbiased manner. The methodologist and the Working Committee scrutinised each step of the review processby accessing the original papers and reviewing the rating of evidence components, and the wording and gradingof each draft evidence statement. As a result, some evidence statements and grades were amended using aWorking Committee consensus approach, and the final evidence statements and grades were agreed.As nutrition is a continuously evolving area and research studies are published on a regular basis, the WorkingCommittee also considered results from high quality studies (primarily systematic reviews) published after theliterature review, and where deemed warranted, included the findings and references in the relevant evidencesections in each chapter. However, only the evidence statements from systematic review of the literature until2009 were graded.112EAT FOR HEALTH – australian dietary guidelinesNational Health and Medical Research Council