title: Standards should be applied in the prevention and handling of missing data for patient-centered outcomes research: a systematic review and expert consensus.
abstract: OBJECTIVE
  To recommend methodological standards in the prevention and handling of missing data for primary patient-centered outcomes research (PCOR).
  
  
  METHODS
  We searched National Library of Medicine Bookshelf and Catalog as well as regulatory agencies' and organizations' Web sites in January 2012 for guidance documents that had formal recommendations regarding missing data. We extracted the characteristics of included guidance documents and recommendations. Using a two-round modified Delphi survey, a multidisciplinary panel proposed mandatory standards on the prevention and handling of missing data for PCOR.
  
  
  RESULTS
  We identified 1,790 records and assessed 30 as having relevant recommendations. We proposed 10 standards as mandatory, covering three domains. First, the single best approach is to prospectively prevent missing data occurrence. Second, use of valid statistical methods that properly reflect multiple sources of uncertainty is critical when analyzing missing data. Third, transparent and thorough reporting of missing data allows readers to judge the validity of the findings.
  
  
  CONCLUSIONS
  We urge researchers to adopt rigorous methodology and promote good science by applying best practices to the prevention and handling of missing data. Developing guidance on the prevention and handling of missing data for observational studies and studies that use existing records is a priority for future research.
authors.affiliation: Center for Clinical Trials, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA. Electronic address: tli@jhsph.edu.
authors.forename: Tianjing
authors.initials: T
authors.lastname: Li
authors.forename: Susan
authors.initials: S
authors.lastname: Hutfless
authors.forename: Daniel O
authors.initials: DO
authors.lastname: Scharfstein
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Daniels
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Hogan
authors.forename: Roderick J A
authors.initials: RJ
authors.lastname: Little
authors.forename: Jason A
authors.initials: JA
authors.lastname: Roy
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Law
authors.forename: Kay
authors.initials: K
authors.lastname: Dickersin
mesh_terms: D035843:Biomedical Research / Q000592:standards*; D032921:Consensus; D006801:Humans; D063868:Patient Outcome Assessment; D012107:Research Design / Q000592:standards*
keywords: Consensus survey; Handling missing data; Methodology standards; Patient-centered outcomes research; Preventing missing data; Systematic review