title: Effect of telephone follow-up on retention and balance in an alcohol intervention trial.
abstract: OBJECTIVE
  Telephone follow-up is not currently recommended as a strategy to improve retention in randomized trials. The aims of this study were to estimate the effect of telephone follow-up on retention, identify participant characteristics predictive of questionnaire completion during or after telephone follow-up, and estimate the effect of including participants who provided follow-up data during or after telephone follow-up on balance between randomly allocated groups in a trial estimating the effect of electronic alcohol screening and brief intervention on alcohol consumption in hospital outpatients with hazardous or harmful drinking.
  
  
  METHODS
  Trial participants were followed up 6 months after randomization (June-December 2013) using e-mails containing a hyperlink to a web-based questionnaire when possible and by post otherwise. Telephone follow-up was attempted after two written reminders and participants were invited to complete the questionnaire by telephone when contact was made.
  
  
  RESULTS
  Retention before telephone follow-up was 62.1% (520/837) and 82.8% (693/837) afterward: an increase of 20.7% (173/837). Therefore, 55% (95% CI 49%-60%) of the 317 participants who had not responded after two written reminders responded during or after the follow-up telephone call. Age < 55 years, a higher AUDIT-C score and provision of a mobile/cell phone number were predictive of questionnaire completion during or after telephone follow-up. Balance between randomly allocated groups was present before and after inclusion of participants who completed the questionnaire during or after telephone follow-up.
  
  
  CONCLUSIONS
  Telephone follow-up improved retention in this randomized trial without affecting balance between the randomly allocated groups.
authors: School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW 2308, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW 2305, Australia.
authors: Natalie A
authors: NA
authors: Johnson
authors: School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW 2308, Australia.
authors: Kypros
authors: K
authors: Kypri
authors: School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW 2308, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW 2305, Australia.
authors: Joanna
authors: J
authors: Latter
authors: School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW 2308, Australia.
authors: Patrick
authors: P
authors: McElduff
authors: School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW 2308, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW 2305, Australia; Department of General Medicine, John Hunter Hospital, New Lambton Heights, NSW 2305, Australia.
authors: John
authors: J
authors: Attia
authors: Department of Community Health Sciences, Boston University School of Public Health, and Clinical Addiction Research and Education Unit, Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA; Boston Medical Center, Boston, MA 02118, USA.
authors: Richard
authors: R
authors: Saitz
authors: Centre for Youth Substance Abuse Research, University of Queensland, Herston, QLD 4006, Australia; Disciplines of Psychiatry and Addiction Medicine, University of Sydney, Sydney, NSW 2006, Australia.
authors: John B
authors: JB
authors: Saunders
authors: School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW 2308, Australia; Hunter New England Local Health District Population Health, Wallsend, NSW 2287, Australia.
authors: Luke
authors: L
authors: Wolfenden
authors: School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW 2308, Australia; Hunter New England Local Health District Drug and Alcohol Clinical Services, Newcastle, NSW 2300, Australia.
authors: Adrian
authors: A
authors: Dunlop
authors: School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW 2308, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW 2305, Australia.
authors: Christopher
authors: C
authors: Doran
authors: Department of Health Sciences, University of York, York, UK.
authors: Jim
authors: J
authors: McCambridge
keywords: Alcohol consumption; Lost to follow-up; Randomized controlled trial; Telephone