NutriGrade: A scoring system to assess and judge the meta-evidence of randomized controlled trials and cohort studies in nutrition research

Lukas Schwingshackl, Sven Knüppel, Carolina Schwedhelm, Georg Hoffmann, Benjamin Missbach, Marta Stelmach-Mardas, Stefan Dietrich, Fabian Eichelmann, Evangelos Kontopantelis, Khalid Iqbal, Krasimira Aleksandrova, Stefan Lorkowski, Michael F. Leitzmann, Anja Kroke, Heiner Boeing

Research output: Contribution to journalArticlepeer-review

Abstract

The objective of this study was to develop a scoring system (NutriGrade) to evaluate the quality of evidence of randomized controlled trial (RCT) and cohort study meta-analyses in nutrition research, building upon previous tools and expert recommendations. NutriGrade aims to assess the meta-evidence of an association or effect between different nutrition factors and outcomes, taking into account nutrition research-specific requirements not considered by other tools. In a pretest study, 6 randomly selected meta-analyses investigating diet-disease relations were evaluated with NutriGrade by 5 independent raters. After revision, NutriGrade was applied by the same raters to 30 randomly selected meta-analyses in the same thematic area. The reliability of ratings of NutriGrade items was calculated with the use of a multirater k, and reliability of the total (summed scores) was calculated with the use of intraclass correlation coefficients (ICCs). The following categories for meta-evidence evaluation were established: high (8-10), moderate (6-7.99), low (4-5.99), and very low (0-3.99). The NutriGrade scoring system (maximum of 10 points) comprises the following items: 1) risk of bias, study quality, and study limitations, 2) precision, 3) heterogeneity, 4) directness, 5) publication bias, 6) funding bias, 7) study design, 8) effect size, and 9) dose-response. The NutriGrade score varied between 2.9 (very lowmeta-evidence) and 8.8 (high meta-evidence) for meta-analyses of RCTs, and it ranged between 3.1 and 8.8 for meta-analyses of cohort studies. The k value of the ratings for each scoring item varied from 0.32 (95% CI: 0.22, 0.42) for risk of bias for cohort studies and 0.95 (95% CI: 0.91, 0.99) for study design, with a mean k of 0.66 (95% CI: 0.53, 0.79). The ICC of the total score was 0.81 (95% CI: 0.69, 0.90). The NutriGrade scoring system showed good agreement and reliability. The initial findings regarding the performance of this newly established scoring system need further evaluation in independent analyses.

Original languageEnglish
Pages (from-to)994-1004
Number of pages11
JournalAdvances in Nutrition
Volume7
Issue number6
DOIs
Publication statusPublished - 1 Nov 2016

Keywords

  • Meta-analysis
  • Meta-evidence
  • Nutrition
  • Reliability
  • Scoring

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