Professionally designed information materials and telephone reminders improved consent response rates: evidence from an RCT nested within a cohort study.
OBJECTIVE
To investigate whether different study-to-participant communication methods increase response, increase response from hard-to-engage individuals, and influence participants' consent decisions.


METHODS
A randomized controlled trial within the Avon Longitudinal Study of Parents and Children. Cohort members were invited to re-enroll at age 18 and consent to linkage to their health and administrative records. Participants were randomized to receive one of eight combinations of three interventions: a prior-notification postcard or no contact, a standard or professionally designed consent pack, and a phone or postal reminder. The primary outcome was return of the consent form ("response"), with consent decision being the secondary outcome.


RESULTS
Of 1,950 participants, 806 (41%) responded. Response rates were 2.7% higher (95% confidence interval: -0.06, 5.5%; P = 0.06) among those receiving designed packs than among those receiving standard packs and 6.4% higher (2.3, 10.6%; P = 0.002) among those receiving phone reminders (compared with postal reminders). The prior-notification postcard did not influence response rates [difference = 0% (-2.8, 2.8%; P = 1.0)], and we found no evidence that the communication method influenced consent decision.


CONCLUSIONS
This trial provides evidence that communication material design can influence response rates and that phone reminders have superior cost/benefit returns over designed materials. Experimental evaluation of communications strategies and dissemination of findings may benefit cohort studies.
ALSPAC, School of Social and Community Medicine, University of Bristol, Oakfield House, Oakfield Grove, Bristol BS8 2BN, UK. Electronic address: a.w.boyd@bristol.ac.uk.
Andy
A
Boyd
ALSPAC, School of Social and Community Medicine, University of Bristol, Oakfield House, Oakfield Grove, Bristol BS8 2BN, UK.
Kate
K
Tilling
ALSPAC, School of Social and Community Medicine, University of Bristol, Oakfield House, Oakfield Grove, Bristol BS8 2BN, UK.
Rosie
R
Cornish
ALSPAC, School of Social and Community Medicine, University of Bristol, Oakfield House, Oakfield Grove, Bristol BS8 2BN, UK.
Amy
A
Davies
ALSPAC, School of Social and Community Medicine, University of Bristol, Oakfield House, Oakfield Grove, Bristol BS8 2BN, UK.
Kerry
K
Humphries
ALSPAC, School of Social and Community Medicine, University of Bristol, Oakfield House, Oakfield Grove, Bristol BS8 2BN, UK.
John
J
Macleod
D000293:Adolescent; D000328:Adult; D004739:England; D005260:Female; D017144:Focus Groups; D006306:Health Surveys; D006801:Humans; D007258:Informed Consent; D008137:Longitudinal Studies; D008297:Male; D008498:Medical Record Linkage; D010358:Patient Participation; D011177:Postal Service; D011247:Pregnancy; D011446:Prospective Studies; D017010:Reminder Systems; D012107:Research Design; D013689:Telephone
ALSPAC; Cohort study; Randomized controlled trial; Record linkage; Recruitment; Retention