Review of the Draft NTP Monograph Systematic Review of Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects (2020) / Chapter Skim
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2 Methods and Presentation
2 Methods and Presentation
Pages 10-21
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From page 10... ...
, the Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental 1Although the protocol for the fluoride monograph refers to both versions of the OHAT handbook, the committee assumes that it was based on the updated version given that it incorporates a revised figure (NTP 2017, Figure 3, p.
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From page 11... ...
statement; development of inclusion and exclusion criteria for study selection; a search of the literature; extraction of data from included studies; critical appraisal of studies for risk of bias; synthesis of results from included studies; and hazard identification by integration of the evidence from human and animal studies and consideration of supporting evidence from mechanistic studies. Ideally, the protocol should follow guidance provided by the OHAT handbook but include details specific to the given systematic review, such as how to rate risk of bias in assessing outcomes of neurodevelopmental and cognitive effects as in the case here.
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From page 12... ...
Given the issues raised here and in later chapters, the committee finds that there are some deficiencies in the protocol and its execution. Role of the OHAT Handbook As discussed, the OHAT handbook outlines "standard operating procedures for systematic review and evidence integration for conducting OHAT literaturebased assessments" (NTP 2019a, p.
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From page 13... ...
• Nomination history. According to the OHAT handbook, this section should describe "the history of the nomination…steps the NTP has taken to solicit feedback on the topic under consideration, including Federal Register notices, requests for information in the NIH Guide for Grants and Contracts, outreach to federal agencies on the NTP Executive Committee, or outreach to other divisions within NIEHS [National Institute of Environmental Health Sciences]
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From page 14... ...
For data extraction, the protocol does not mention training for data extractors or pilot testing of all team members as recommended in the OHAT handbook. To increase transparency, NTP should clearly describe the role of the OHAT handbook in developing the systematic-review protocol primarily to set expectations for how closely the process described in the handbook will be followed in the protocol and eventually the systematic review.
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From page 15... ...
However, it is unclear how the updated search specifically for animal studies was conducted and whether the modifications in search strategy resulted in the identification of new studies published before 2016. The monograph discusses the search strategies to some extent by stating that "literature searches for this systematic review were conducted independent of the literature search conducted for the NTP (2016)
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From page 16... ...
The OHAT handbook mentions the SWIFT text-mining and machine-learning tools but does not justify or cite why 98% estimated recall is considered sufficient. The committee recommends that the protocol discuss the basis of that decision and potentially conduct a sensitivity analysis to determine the effect of that cutoff on the overall findings (for example, by reviewing a random subset of the studies excluded on the basis of the SWIFT algorithm to identify the number of potentially missed references)
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From page 17... ...
. However, the monograph differs by stating that "if mechanistic data provide strong opposition for biological plausibility of the relationship between exposure and the health effect, the hazard identification conclusion may be downgraded…from that initially derived" (NTP 2019c, p.
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From page 18... ...
It might be better to organize the studies in a more informative way; for example, risk-of-bias tables could be organized by risk-of-bias ratings (that is, studies that have the most green "ratings" first and studies that have fewer such ratings thereafter) or by stratifying the studies according to critical risk-of-bias domains similar to the example provided in the OHAT handbook (NTP 2015, p.
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From page 19... ...
NTP should consider supplementing Table 7 with clear justification for each confidence factor rationale for and why upgrade and downgrade factors were not applied for any of the human evidence. Finally, there is little discussion of the process for obtaining missing or additional information from study authors.
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From page 20... ...
2015. New OHAT Handbook for Conducting Systematic Reviews.
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From page 21... ...
2019a. Handbook for Conducting a Literature-Based Health Assessment Using OHAT Approach for Systematic Review and Evidence Integration.
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