Assessment of changes to screening programmes: Why randomisation is important

Date of this Version


Document Type

Journal Article

Publication Details

Citation only

Bell, K., Bossuyt, P., Glasziou, P. &, Irwig, L. (2015). Assessment of changes to screening programmes: Why randomisation is important. The BMJ, 350, 1-4.

Access the journal

© Copyright, BMJ Publishing Group Ltd, 2015




Randomised controlled trials provide the best evidence of the benefits and harms of screening. Yet, once a screening programme is started, uncertainty may remain about specific components of the strategy. For example, what test should we use to screen for colorectal cancer? How long should we wait before re-screening? Should potential participants be given an information booklet? The screening technology itself is continually evolving and often there is uncertainty about to whether to introduce new testing methods, such as liquid based cytology for cervical cancer1 or 3D mammography to screen for breast cancer.2

We believe that such decisions should be based on the strongest available evidence. This requires pragmatic trials within the screening programme, with the eligible population randomised to different screening strategies. Here, we use the example of bowel cancer screening to show why randomisation is needed and how it can work. However, the general principles can be applied to population screening for other conditions.

This document is currently not available here.



This document has been peer reviewed.