title: Reporting missing participant data in randomised trials: systematic survey of the methodological literature and a proposed guide.
abstract: OBJECTIVE
  We conducted a systematic survey of the methodological literature to identify recommended approaches for how and what randomised clinical trial (RCT) authors should report on missing participant data and, on the basis of these approaches, to propose guidance for RCT authors.
  
  
  METHODS
  We defined missing participant data (MPD) as missing outcome data for trial participants. We considered both categorical and continuous outcome data. We searched MEDLINE and the Cochrane Methodology Register for articles in which authors proposed approaches to reporting MPD from RCTs. We selected eligible articles independently and in duplicate and extracted data in duplicate. Using an iterative process of discussion and revisions, we used the findings to develop guidance.
  
  
  RESULTS
  Of 10,501 unique citations identified, 13 articles reporting on 10 approaches proved eligible. The identified approaches recommend reporting the following aspects (from most to least frequently recommended): number of participants with MPD (n=10), reasons for MPD (n=7), methods used to handle MPD in the analysis (n=4), flow of participants (n=3), pattern of missingness (eg, whether at random) (n=3), differences in rates of MPD between trial arms (n=2), differences between participants with and without MPD (n=2), results of any sensitivity analyses (n=2), implication of MPD on interpreting the results (n=2) and methods used to prevent missing data (n=1). We propose a guide with nine items related to reporting the number, reasons, patterns, analytical methods and interpretation of MPD.
  
  
  CONCLUSIONS
  Most identified approaches invite trial authors to report the extent of MPD and the underlying reasons. Fewer approaches focus on reporting missingness patterns, methods for handling MPD and implications of MPD on results. Our proposed guidance could help RCT authors to better report, and readers to better identify participants with missing data.
authors.affiliation: Department of Internal Medicine, American University of Beirut, Beirut, Lebanon Faculty of Health Sciences, American University of Beirut, Beirut, Lebanon Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Elie A
authors.initials: EA
authors.lastname: Akl
authors.affiliation: Department of Internal Medicine, American University of Beirut, Beirut, Lebanon.
authors.forename: Khaled
authors.initials: K
authors.lastname: Shawwa
authors.affiliation: Department of Internal Medicine, American University of Beirut, Beirut, Lebanon Faculty of Health Sciences, American University of Beirut, Beirut, Lebanon.
authors.forename: Lara A
authors.initials: LA
authors.lastname: Kahale
authors.affiliation: Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Agoritsas
authors.affiliation: Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada Evidence Based Dentistry Unit, Faculty of Dentistry, Universidad de Chile, Santiago, Chile Institute of Health Policy, Management & Evaluation, University of Toronto, Toronto, Canada.
authors.forename: Romina
authors.initials: R
authors.lastname: Brignardello-Petersen
authors.affiliation: Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada Department of Anesthesia, McMaster University, Hamilton, Canada The Michael G. DeGroote Institute for Pain Research and Care, McMaster University, Hamilton, Canada.
authors.forename: Jason W
authors.initials: JW
authors.lastname: Busse
authors.affiliation: Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada Evidence Based Dentistry Unit, Faculty of Dentistry, Universidad de Chile, Santiago, Chile.
authors.forename: Alonso
authors.initials: A
authors.lastname: Carrasco-Labra
authors.affiliation: Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada Department of Anesthesia, McMaster University, Hamilton, Canada Department of Anesthesia & Pain Medicine, the Hospital for Sick Children, Toronto, Canada Department of Medicine, Stanford Prevention Research Center, Stanford University, Palo Alto, USA.
authors.forename: Shanil
authors.initials: S
authors.lastname: Ebrahim
authors.affiliation: Institute of Health Policy, Management & Evaluation, University of Toronto, Toronto, Canada Department of Anesthesia & Pain Medicine, the Hospital for Sick Children, Toronto, Canada.
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Johnston
authors.affiliation: Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada Department of Internal Medicine, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Neumann
authors.affiliation: Iberoamerican Cochrane Centre, Biomedical Research Institute Sant Pau-CIBER of Epidemiology and Public Health (CIBERESP- IIB Sant Pau), Barcelona, Spain.
authors.forename: Ivan
authors.initials: I
authors.lastname: Sola
authors.affiliation: Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada Clinical Research and Evaluation Unit, Chinese Evidence-based Medicine Center, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Sun
authors.affiliation: Norwegian Knowledge Centre for the Health Services, Oslo, Norway Department of Medicine, Innlandet Hospital Trust, Gjøvik, Norway.
authors.forename: Per
authors.initials: P
authors.lastname: Vandvik
authors.affiliation: Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Yuqing
authors.identifier: http://orcid.org/0000-0002-6318-3575
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Iberoamerican Cochrane Centre, Biomedical Research Institute Sant Pau-CIBER of Epidemiology and Public Health (CIBERESP- IIB Sant Pau), Barcelona, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Alonso-Coello
authors.affiliation: Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Gordon H
authors.initials: GH
authors.lastname: Guyatt
mesh_terms: D015982:Bias; D000068598:Data Accuracy; D017408:Guidelines as Topic; D006801:Humans; D010352:Patient Dropouts / Q000706:statistics & numerical data*; D016032:Randomized Controlled Trials as Topic; D012107:Research Design / Q000706:statistics & numerical data*
keywords: EPIDEMIOLOGY; Missing participant data; Randomized clinical trials; Systematic reviews