Three controlled trials of interventions to increase recruitment to a randomized controlled trial of mobile phone based smoking cessation support.
BACKGROUND
Recruitment is a major challenge for trials but there is little evidence regarding interventions to increase trial recruitment. We report three controlled trials of interventions to increase recruitment to the Txt2stop trial.


OBJECTIVE
To evaluate: Trial 1. The impact on registrations of a text message regarding an online registration facility; Trial 2. The impact on randomizations of sending pound5 with a covering letter to those eligible to join the trial; Trial 3. The impact on randomizations of text messages containing quotes from existing participants.


METHODS
Single blind controlled trials with allocation concealment.


METHODS
Trial 1: A text message regarding our new online registration facility; Trial 2: A letter with pound5 enclosed; Trial 3: A series of four text messages containing quotes from participants. The control group in each trial received standard Txt2stop procedures.


RESULTS
Trial 1: 3.6% (17/470) of the intervention group and 1.1% (5/467) of the control group registered for the trial, risk difference 2.5% (95% CI 0.6-4.5). 0% (0/ 470) of the intervention group and 0.2% (1/467) of the control group registered successfully online, risk difference -0.2 (95% CI -0.6-0.2); Trial 2: 4.5% (11/246) of the intervention group and 0.4% (1/245) of the control group were randomized into the Txt2stop trial, risk difference 4.0% (95% CI 1.4-6.7); Trial 3: 3.5% (14/405) of the intervention group and 0% (0/406) of the control group were randomized into the Txt2stop trial, risk difference 3.5 (95% CI 1.7-5.2).


CONCLUSIONS
There were no baseline data available for trial 1. Allocation of participant IDs in trials 2 and 3 were systematic.


CONCLUSIONS
Sending a text message about an online registration facility increased registrations to Txt2stop, but did not increase online registrations. Sending a pound5 reimbursement for participants' time and sending text messages containing quotes from existing participants increased randomizations into the Txt2stop trial. Clinical Trials 2010; 7: 265-273. http://ctj.sagepub.com.
Free
Caroline
C
NPHIRU, LSHTM, London, UK. caroline.free@lshtm.ac.uk
Hoile
Elizabeth
E
Robertson
Steven
S
Knight
Rosemary
R
D000328:Adult; D040421:Cell Phone; D003142:Communication; D006801:Humans; D008875:Middle Aged; D018579:Patient Selection; D016540:Smoking Cessation / Q000379:methods*; D012944:Social Support; D006113:United Kingdom