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  • Poster presentation
  • Open Access

The NICOLA recruitment trial (NICOLA-RT): can you improve recruitment by making zero cost amendments to the invitation letter?

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Trials201516 (Suppl 2) :P106

  • Published:


  • Public Health
  • Cohort Study
  • Final Analysis
  • Trial Registration
  • Potential Participant


NICOLA-RT is using minor edits to invitation letters to assess their impact on potential participants’ decisions about joining a prospective study. Even small improvements in recruitment could produce important savings in cost and time. The elements in NICOLA-RT have been registered as SWAT (Study Within A Trial) 3, 4 and 5. These SWAT examine different approaches to recruitment and retention and ways to maximise these.

Aims and objectives

NICOLA-RT examines the impact of differing invitation letters on study recruitment, with the following specific objectives: assessing if the gender of the person signing the letter affects recruitment; assessing the impact of describing the research as a ‘study’ or ‘project’ and assessing if including an explicit statement about confidentiality for the participants in the invitation letter has an impact.


The study is a 3x2x2 factorial randomised trial of different invitation letters. It is embedded in the ongoing NICOLA cohort study, and tests three different signatures (male, female and the trial group), the use of ‘study’ versus ‘project’ and the presence or absence of an explicit statement about confidentiality.


Recruitment for the NICOLA cohort began in January 2014 and is expected to continue until late 2015. Although the cohort is still recruiting, this presentation will detail preliminary findings from the interim analysis of more than 7700 letters, which have revealed no significant differences to date.


Recruitment is continuing until NICOLA recruits 8,500 participants and a final analysis of NICOLA-RT will be conducted at that stage.

Trial Registration


Authors’ Affiliations

Queen's University Belfast, Belfast, UK
University of Liverpool, Liverpool, UK


© Maguire et al. 2015

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.


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