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Recruitment and retention strategies and the examination of attrition bias in a randomised controlled trial in children's centres serving families in disadvantaged areas of England

Hindmarch, Paul; Hawkins, Adrian; McColl, Elaine; Hayes, Mike; Majsak-Newman, Gosia; Ablewhite, Joanne; Deave, Toity; Kendrick, Denise


Paul Hindmarch

Adrian Hawkins

Elaine McColl

Mike Hayes

Gosia Majsak-Newman

Joanne Ablewhite

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Toity Deave
Associate Professor in Child & Family Health

Denise Kendrick


© 2015 Hindmarch et al. Background: Failure to retain participants in randomised controlled trials and longitudinal studies can cause significant methodological problems. We report the recruitment and retention strategies of a randomised controlled trial to promote fire-related injury prevention in families with pre-school children attending children's centres in disadvantaged areas in England. Methods: Thirty-six children's centres were cluster randomised into one of three arms of a 12-month fire-related injury prevention trial. Two arms delivered safety interventions and there was one control arm. Retention rates compared the numbers of participants responding to the 12-month questionnaire to the number recruited to the trial. Multivariable random effects logistic regression was used to explore factors independently associated with participant retention. Results: The trial exceeded its required sample size through the use of multiple recruitment strategies. All children's centres remained in the study, despite increased reorganisation. Parent retention was 68% at 12 months, ranging from 65% to 70% across trial arms and from 62% to 74% across trial sites. There was no significant difference in the rates of retention between trial arms (p = 0.58) or between trial sites (p = 0.16). Retention was significantly lower amongst mothers aged 16-25 years than older mothers [adjusted odds ratio (AOR) 0.57, 95% CI 0.41, 0.78], those living in non-owner occupied accommodation than in owner occupied accommodation (AOR 0.53, 95% CI 0.38, 0.73) and those living in more disadvantaged areas (most versus least disadvantaged quintiles AOR 0.50, 95% CI 0.30, 0.82). Conclusions: Studies recruiting disadvantaged populations should measure and report attrition by socioeconomic factors to enable determination of the extent of attrition bias and estimation of its potential impact on findings. Where differential attrition is anticipated, consideration should be given to over-sampling during recruitment and targeted and more intensive strategies of participant retention in these sub-groups. In transient populations collection of multiple sources of contact information at recruitment and throughout the study may aid retention. Trial registration: identifier: NCT01452191; Date of registration: 10 October 2011, ISRCTN65067450.


Hindmarch, P., Hawkins, A., McColl, E., Hayes, M., Majsak-Newman, G., Ablewhite, J., …Kendrick, D. (2015). Recruitment and retention strategies and the examination of attrition bias in a randomised controlled trial in children's centres serving families in disadvantaged areas of England. Trials, 16(1),

Journal Article Type Article
Publication Date Mar 1, 2015
Journal Trials
Print ISSN 1745-6215
Publisher BMC
Peer Reviewed Peer Reviewed
Volume 16
Issue 79
Keywords retention strategies, attrition bias, RCT, injury prevention, pre-school, children’s centres
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