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Critical appraisal of a randomized trial of a preventive agent 

Critical appraisal of a randomized trial of a preventive agent
Chapter:
Critical appraisal of a randomized trial of a preventive agent
Author(s):

Mark Elwood

DOI:
10.1093/med/9780199682898.003.0013
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date: 20 September 2019

This chapter presents an important, large, international randomised trial of prevention, the use of folic acid and multivitamins in preventing spina bifida and other neural tube defects. This shows the ethical and logistic issues involved, a factorial randomised design, a sequential analysis and early stopping example, and specificity of effect, and discusses the application to policy. The critical assessment follows the scheme set out in chapter 10: describing the study, assessing the non-causal explanations of observation bias, confounding, and chance variation; assessing time relationships, strength, dose-response, consistency and specificity, and applying the results to the eligible, source, and target populations; and then comparing the results with evidence from other studies, considering consistency and specificity, biological mechanisms, and coherence with the distribution of exposures and outcomes. The chapter gives a summary and table of the critical assessment and its conclusions; and comments on the impact of the study and research carried out since.

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