Background

Gestational diabetes mellitus (GDM) is a special form of diabetes in women of child-bearing age and is a common gestational endocrine disease [1]. Due to its increasing prevalence, GDM results in significant short- and long-term impairments in the individual’s health and their offspring’s health [Assessment of consistency

A total of 361 original recommendations for GDM management which were from 14 guidelines were included. Although some recommendations did not fall into any of the identified themes, we undertook consistency appraisal of these as well. As presented in Table 5, different guidelines appeared to have significant discrepancies in consistency of guideline content. Even in the same guideline, consistency differed in three aspects: ①consistency between search strategy and selection of evidence, ②consistency between selected evidence and interpretation, and ③consistency between interpretations and resulting recommendations. Among all guidelines included, NICE guidelines showed the best average score of consistency in each aspect. However, HKCOG guidelines and CMA guidelines received extremely low scores in each aspect. Apparently, in this study, evidence-based guidelines rated relatively higher in content consistency than expert consensus-based guidelines. Consistency appraisal of each guideline is presented in Fig. 2. For consistency in each aspect, most guidelines showed the same tendency, that is, a guideline which received high average scores could also receive high scores in the other two aspects, and, conversely, low average scores in all aspects. When it came to all recommendations, search strategy and selection of evidence were slightly inconsistent. The radar chart showing comparable consistency between search strategy and selection of evidence, between selected evidence and interpretation, and between interpretation and resulting recommendations (scilicet 49.31, 57.20 and 58.17%, respectively) is presented in Fig. 3.

Table 5 Consistency characteristics of guidelines
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Fig. 2
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Consistency appraisal of guidelines

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Fig. 3
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Consistency appraisal in all recommendations

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Discussion

Gestational diabetes mellitus is a challenging complication of pregnancy that many women and doctors struggle with. In this review, we examined the existing guidelines on the management for GDM in 11 countries or regions. Given that appropriate methodologies and rigorous strategies in the guideline development process are crucial for guideline implementation [25], the development methods of the guidelines were measured using the AGREE II instrument. In general, the quality of GDM guidelines, especially evidence-based guidelines, was high. This could be explained by the fact that much progress has been made in the development of methodological and reporting criteria of evidence-based guidelines within the past decade [30]. Nonetheless, as the results in previous study revealed, the domains of Rigor of Development, Stakeholder Involvement and, Editorial Independence still need to be improved [26].

It is noted that practice guidelines with the best methodological quality were not necessarily the most valid in their recommendations [27]. Thus it is important to emphasize that clinical practitioners should critically evaluate the methodological quality as well as the content of the recommendations before adopting the recommendations, which leads to another issue, that is, consistency appraisal. Despite many researchers being aware of the crucial role of the appraisal of consistency between evidence and resulting recommendations, there are no existing criteria for assessing content consistency of guidelines. In guideline adaptation of some topics, qualitative analysis was used in content extraction, which formulated a general description of the research topic through generating categories without any consistency appraisal [31, 32]. In this review, we developed a “recommendation matrix” on the basis of the CAN-Implement© method [33], and used the tool to extract and assess guideline content. As a recommendation matrix was used, not only relevant and potentially relevant recommendations on all pre-specified healthcare aspects for GDM care were identified, but also consistency between search strategy and selection of evidence, between selected evidence and interpretation, and between interpretation and resulting recommendations was assessed. The results showed that current guidelines on GDM care are of varied consistency, and guidelines developed in internationally recognized guideline development methodology show better consistency. Also guidelines that have low consistency in one aspect may also have low consistency in other two aspects. This is probably because reporting quality of guidelines is the cornerstone of consistency assessment. Those guidelines with evidence tables or technical reports not published may also show low consistency. Thus, guideline development committees are strongly encouraged to make use of guideline development manuals when drafting guidelines.

Regarding guideline content, five aspects were analyzed: diagnosis of GDM, prenatal care, intrapartum care, neonatal care, and postpartum care. Most recommendations in guidelines focused on prenatal care, especially all kinds of therapies that might reduce the risk of adverse pregnancy outcomes related to uncontrolled blood sugar pre-conception. This review generated similar results with those from a previous study that international guidelines were consistent in most of their recommendations [34]. Nonetheless, although commonality in most areas existed, there were still some discrepancies among guidelines. For example, recommendations regarding oral hypoglycemic agents in the guidelines diverged. Some guidelines recommended that oral hypoglycemic agents be considered as an initial pharmacological intervention, while some guidelines only considered insulin as an exclusive hypoglycemic medicine. Guidelines were supported with evidence, so inconsistency may be caused by insufficient evidence on pharmacological interventions in the period in which the guidelines were developed [26]. However, it should be reminded that even though all evidence available was identified, consensus usually did not warrant similar recommendations in different contexts. This was because when a recommendation was developed, not only available evidence, but benefits and harms, patients’ values and preferences, as well as resource implications, should be appropriate considered [10].

Since recommendations were well summarized, guideline adaptation was required to maintain the validity of recommendations in different health care systems. Guideline adaptation involves using knowledge synthesis of existing guidelines to produce recommendations, rather than relying only on a review of primary literature, for the purpose of reducing duplication of effort [35]. In mainland China and Hong Kong, there were only expert consensus for GDM care [22, 23], without a national GDM management evidence-based guideline adapted to the Chinese context previously. In this instance, it is recommended to adapt the clinical practice guideline related to GDM management for the local context, providing support for professionals to make better decisions in clinical practice. How to select, tailor and implement recommendations and supporting evidence extracted is the next challenging step.

Limitation

Due to the language barriers, we only included guidelines in English and Chinese. As a result, we only got existing guidelines on the management for GDM in 11 countries or regions in this review. And yet, we have no idea whether other countries use the recommendations provided by a certain guideline or use recommendations developed in their own language.

Another key limitation of this study is the subjectivity in appraising the consistency between evidence and recommendations. Although we attempted to minimize these discrepancies by stating the assessment criteria and through rigorous discussion, the results of the consistency appraisal still varied because of different understandings between researchers. Additionally, reporting quality of some guidelines is not clear cut, which was another barrier in the process of content analysis. Apart from this, this is the first time that we used a “recommendation matrix” in content analysis, and the tool we developed may still need to be modified.

Conclusion

This paper describes the process used to extract and access the content of guidelines for GDM management. In conclusion, the recommendations were developed in five aspects: diagnosis of GDM, prenatal care, intrapartum care, neonatal care and postpartum care. The consistency of guidelines on the management of GDM in pregnancy is highly variable and this inconsistency needs to be addressed. Also, this review has proven that a “recommendation matrix” can be a tool to extract and assess consistency of guidelines. Additionally, our findings indicated that it is necessary to adapt and disseminate easily understandable evidence-based guidelines based on knowledge synthesis of existing guidelines in this paper.