The link will take you to an abstract of the article. NHS staff wishing to obtain a copy of the full text should contact their health care library.   This article has been selected for inclusion in NHS Evidence because it meets the NHS Evidence definition of a major RCT. This is an RCT which has been published in a journal which conforms to the CONSORT criteria, or one that has been appraised and selected by a group of experts for inclusion in an Evidence Update.