Show Summary Details
Page of

Critical appraisal of a randomized trial of a preventive agent 

Critical appraisal of a randomized trial of a preventive agent
Critical appraisal of a randomized trial of a preventive agent

Mark Elwood

Page of

PRINTED FROM OXFORD MEDICINE ONLINE ( © Oxford University Press, 2020. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy and Legal Notice).

date: 22 September 2020

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.

Access to the complete content on Oxford Medicine Online requires a subscription or purchase. Public users are able to search the site and view the abstracts for each book and chapter without a subscription.

Please subscribe or login to access full text content.

If you have purchased a print title that contains an access token, please see the token for information about how to register your code.

For questions on access or troubleshooting, please check our FAQs, and if you can't find the answer there, please contact us.