title: Contacting authors to retrieve individual patient data: study protocol for a randomized controlled trial.
abstract: BACKGROUND
  Individual patient data (IPD) meta-analysis is considered the "gold standard" for exploring the effectiveness of interventions in different subgroups of patients. However, obtaining IPD is time-consuming and contact with the researchers responsible for the original trials is usually required. To date, there are no studies evaluating different strategies to optimize the process for retrieval of IPD from such researchers. Our aim is to examine the impact of providing incentives to the researchers responsible for the trials eligible for a meta-analysis to submit their IPD.
  
  
  METHODS
  We updated our previously published systematic reviews for type 1 diabetes mellitus comparing long- and intermediate-acting insulin regimens (from January 2013 to June 2015) and for Alzheimer's dementia comparing cognitive enhancers (from January 2015 to May 2015). Eligible were randomized controlled trials (RCTs) fulfilling the eligibility criteria of the systematic reviews. We will randomly allocate authors of the reports of these RCTs into an intervention or control group. Those allocated to the intervention group will be contacted by email, mail, and phone, and will be asked to provide the IPD from their RCT and will be given a financial incentive. Those allocated to the control group will be contacted by email, mail, and phone, but will not receive a financial incentive. Our primary outcome will be the proportion of authors who provide the IPD. The secondary outcomes will be the time to return the dataset (defined as the period between the information request and the authors' response with the dataset), and completeness of data. We will compare the response rates in the two groups using the odds ratio and the corresponding 95 % confidence interval. We will also use binary logistic regression and cox regression analyses to examine whether different RCT characteristics, such as study size and sponsor information, influence the probability of providing IPD and the time needed to share the data.
  
  
  CONCLUSIONS
  This study will determine whether a financial incentive affects response rates when seeking IPD from the original researchers. We will disseminate our findings in an open access scientific journal and present results at national and international conferences.
  
  
  BACKGROUND
  This trial is registered in Clinical Trials.gov, ID number NCT02569411 . Date of registration 5 October 2015.
authors.affiliation: Li Ka Shing Knowledge Institute of St. Michael's Hospital, 209 Victoria Street, East Building, Toronto, ON, M5B 1T8, Canada.
authors.forename: Areti Angeliki
authors.initials: AA
authors.lastname: Veroniki
authors.affiliation: Li Ka Shing Knowledge Institute of St. Michael's Hospital, 209 Victoria Street, East Building, Toronto, ON, M5B 1T8, Canada.|Department of Geriatric Medicine, University of Toronto, Toronto, ON, Canada.
authors.forename: Sharon E
authors.initials: SE
authors.lastname: Straus
authors.affiliation: Li Ka Shing Knowledge Institute of St. Michael's Hospital, 209 Victoria Street, East Building, Toronto, ON, M5B 1T8, Canada.
authors.forename: Huda
authors.initials: H
authors.lastname: Ashoor
authors.affiliation: Centre for Reviews and Dissemination, University of York, York, UK.
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Stewart
authors.affiliation: Northern Ireland Hub for Trials Methodology Research, Queen's University Belfast, Belfast, UK.
authors.forename: Mike
authors.initials: M
authors.lastname: Clarke
authors.affiliation: Li Ka Shing Knowledge Institute of St. Michael's Hospital, 209 Victoria Street, East Building, Toronto, ON, M5B 1T8, Canada. triccoa@smh.ca.|Epidemiology Division, Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada. triccoa@smh.ca.
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Tricco
mesh_terms: D001319:Authorship; D003142:Communication; D035881:Compensation and Redress; D034742:Electronic Mail; D006801:Humans; D016247:Information Storage and Retrieval / Q000379:methods*; D015201:Meta-Analysis as Topic; D009042:Motivation; D012107:Research Design; D013689:Telephone
keywords: Data collection; Data retrieval; Incentive; Individual participant data; Individual patient data; Meta-analysis; Patient-level data; Response rate