title: US Food and Drug Administration documents can provide unpublished evidence relevant to systematic reviews.
abstract: OBJECTIVE
  A key systematic review (SR) methodology is comprehensive searching. The Drug Effectiveness Review Project (DERP) SRs search US Food and Drug Administration (FDA) documents to identify unpublished evidence. This study evaluates the success of those efforts.
  
  
  METHODS
  We examined DERP reports published since 2003 for the use of FDA preapproval and postmarketing documents. We categorized evidence as (1) unique unpublished studies, (2) supplemental unpublished data, or (3) FDA postmarketing data analysis. Three reviewers independently assigned predetermined impact categories (e.g., qualitative or quantitative usage, fills gaps, confirms findings, and alters conclusions), resolving disagreements through consensus.
  
  
  RESULTS
  Among 114 DERP reports, 19% included unpublished studies and/or supplemental data and 10% included postmarketing analyses. From 175 preapproval documents, 14% provided eligible unpublished studies and 4.0% supplemental unpublished data that helped confirm previous findings, identify important harms, and fill gaps in knowledge about understudied subpopulations, outcomes, and comparisons. Report conclusion statements changed in 9 of 33 instances of premarketing documents compared with 4 of 12 postmarketing analyses.
  
  
  CONCLUSIONS
  The FDA documents can provide important unpublished evidence for SRs, although in a small proportion of cases. Future research should identify attributes that predict which reviews may benefit most from review of FDA documents.
authors.affiliation: Department of Medical Informatics & Clinical Epidemiology, and Oregon Evidence-Based Practice Center, Oregon Health & Science University, Portland, OR, USA. mcdonagh@ohsu.edu
authors.forename: Marian S
authors.initials: MS
authors.lastname: McDonagh
authors.forename: Kim
authors.initials: K
authors.lastname: Peterson
authors.forename: Howard
authors.initials: H
authors.lastname: Balshem
authors.forename: Mark
authors.initials: M
authors.lastname: Helfand
mesh_terms: D004282:Documentation; D017277:Drug Approval; D004358:Drug Therapy; D006801:Humans; D011358:Product Surveillance, Postmarketing; D017594:Publication Bias; D012196:Review Literature as Topic; D014481:United States; D014486:United States Food and Drug Administration
keywords: Drug therapy; Food and Drug Administration; Publication bias; Reporting bias; Systematic reviews; Unpublished evidence