Article
Integrating evidence from randomised controlled trials and cohort studies in nutrition evidence syntheses: application of the novel GRADE guidance
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Authors
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Julia Stadelmaier
- Institute for Evidence in Medicine, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Deutschland
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Gina Bantle
- Institute for Evidence in Medicine, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Deutschland
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Carlos Cuello-Garcia
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Kanada
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Holger J. Schuenemann
- Clinical Epidemiology and Research Center, Department of Biomedical Sciences, Humanitas University & Research Hospital, Humanitas University, Italien
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Joerg J. Meerpohl
- Institute for Evidence in Medicine, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Deutschland; Cochrane Germany, Cochrane Germany Foundation, Deutschland
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Lukas Schwingshackl
- Institute for Evidence in Medicine, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Deutschland
| Published: | March 27, 2025 |
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Outline
Text
Background/research question: The GRADE Working Group published recently new guidance for the integration of randomised controlled trials (RCTs) and non-randomised studies in evidence syntheses [1]. Our study aims to explore the application of this guidance by using prospective cohort studies in nutrition evidence syntheses as replacement, complementary or sequential evidence of RCTs.
Methods: We took a representative sample of body of evidence-pairs of nutrition RCTs and cohort studies investigating similar PI/ECO (population, intervention/exposure, comparison, outcome) questions.
First, we rated the certainty of evidence (CoE) for the bodies of evidence from RCTs. Second, to identify replacement evidence for RCTs, we assessed the CoE of the matched bodies of evidence from cohort studies. Third, we evaluated the congruency of effect estimates, before using cohort evidence as complementary or sequential evidence. In case of similar judgments, we explored the effects of RCTs and cohort studies in pooled estimates using subgroups.
Results: We included 26 body of evidence-pairs. In 14/26 (54%) pairs, the CoE was higher for RCTs: high vs. moderate (n=2), high vs. low (n=1), moderate vs. low (n=4), moderate vs. very low (n=3), low vs. very low (n=4). In 5/26 (19%) pairs, the CoE was higher for cohort studies: moderate vs. low (n=4), low vs. very low (n=1). For six pairs (23%), the CoE was rated as “low” (downgraded for risk of bias and imprecision), and due to congruency, effect estimates were pooled, mitigating imprecision in two evidence pairs. For one pair (4%), the CoE was rated as “very low“, making pooling inappropriate.
Conclusion: This example application provides practical knowledge on the usage of the new GRADE guidance for authors that include both RCT and cohort studies in evidence synthesis.
Competing interests: CCG, HJS, JJM, and LS are members of the GRADE working group. JS and GB have no relevant financial or non-financial interest to disclose.
References
- 1.
- Cuello-Garcia CA, Santesso N, Morgan RL, et al. GRADE guidance 24 optimizing the integration of randomized and non-randomized studies of interventions in evidence syntheses and health guidelines. J Clin Epidemiol. 2022 Feb;142:200-208. DOI: 10.1016/j.jclinepi.2021.11.026
