Why meta-analyses of nutrition interventions in Chinese journals have plenty of room for improvement
This was a key conclusion of a new study, which assessed vitamin interventions to evaluate the overall methodological and reporting qualities of meta-analyses on nutrition published in Chinese journals.
They looked into four Chinese databases from inception until September 2016 for all meta-analyses of vitamin intervention, assessing methodological and reporting qualities via A Measurement Tool to Assess Systematic Reviews (AMSTAR) and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statements, respectively.
Worrying patterns
They used a total of 43 meta-analyses, though none of them had been updated after being published. They focused mainly on the impact of interventions involving vitamins D and E, as well as B vitamins, with the most studied conditions being endocrine, nutritional and metabolic diseases such as obesity, diabetes, and nutritional rickets.
They then reported that the median AMSTAR score was 6 out of 11, and the median PRISMA score was 18 out of 27, with none of the meta-analyses providing an ‘a priori’ design, a list of excluded studies, or a statement on conflict of interest.
The AMSTAR criteria requires an ‘a priori’ design, with the research question and inclusion criteria to be ascertained before a review is conducted.
The current study stated that the abscence of this could be due to an omission in paper-writing, as opposed to all studies lacking an ‘a priori’ design.
Moreover, Chinese journals impose a limitation on paper length, which could explain why the included meta-analyses did not provide a list of excluded studies. This could have in turn increased the risk of selective reporting and therefore, bias.
Only 4.5% of meta-analyses of observational studies published in Chinese journals were found to have stated a conflict of interest.
The study further stated that “funding sources may influence the quality and outcome of meta-analyses”, making the statement on conflict of interest essential, as it can help readers make an informed evaluation of the results.
When it came to the PRISMA checklists, the item for providing a structured abstract was the second poorest among the meta-analyses in this study.
In fact, despite all the studies containing structured summaries, less than 50% of the meta-analyses stated the publication status or included an adequate structure summary, meaning they fell below the international standards for abstract reporting.
The study also advised authors to describe potential biases across studies to lower the risk of bias affecting the results of cumulative evidence.
The PRISMA checklists also recommend that study authors clearly state any funding they may have received to conduct reviews, or state if the review was not funded.
Other PRISMA guidelines include meta-analyses authors being required to describe study limitations, as well as provide sound advice for future research, which could in turn improve reporting quality.
Analysing for the future
The study’s authors also acknowledged its limits, one of which was that the meta-analyses of vitamin interventions were restricted to those published only in Chinese journals.
The study was also focused solely on articles about vitamin interventions, which prompted the authors to write that “the quality of meta-analyses concerning other nutrients” should be assessed in future studies.
They concluded: “The present study provides a comprehensive assessment of a large sample of meta-analyses of vitamin interventions, published in Chinese journals.
“The effective treatment of methylcobalamin on diabetic peripheral neuropathy and the preventive effects of folic acid on stroke have been demonstrated by meta-analyses with higher methodological and reporting quality.
“However, the quality of meta-analyses regarding vitamin interventions should be improved, and an update of the included reviews is necessary to increase the value of the existing meta-analyses. This study strongly recommends that authors and editors use the methodological and reporting guidelines for improving the quality of meta-analyses.”
Source: Asia Pacific Journal of Clinical Nutrition
https://doi.org/10.6133/apjcn.052017.02
“The quality of evidence on nutrition intervention published in Chinese journals: an assessment of meta-analyses on vitamin interventions”
Authors: Yanhua Ning, et al.
