title: A new classification of spin in systematic reviews and meta-analyses was developed and ranked according to the severity.
abstract: We aimed to (1) identify and classify spin (i.e., a description that overstates efficacy and/or understates harm) in systematic reviews and (2) rank spin in abstracts of systematic reviews according to their severity (i.e., the likelihood of distorting readers' interpretation of the results).
  
  
  
  First, we used a four-phase consensus process to develop a classification of different types of spin. Second, we ranked the types of spin in abstracts according to their severity using a Q-sort survey with members of the Cochrane Collaboration.
  
  
  
  We identified 39 types of spin, 28 from the main text and 21 from the abstract; 13 were specific to the systematic review design. Spin was classified into three categories: (1) misleading reporting, (2) misleading interpretation, and (3) inappropriate extrapolation. Spin ranked as the most severe by the 122 people who participated in the survey were (1) recommendations for clinical practice not supported by findings in the conclusion, (2) misleading title, and (3) selective reporting.
  
  
  
  This study allowed for identifying spin that is likely to distort interpretation. Our classification could help authors, editors, and reviewers avoid spin in reports of systematic reviews.
authors: Centre de Recherche Épidémiologie et Statistique Sorbonne Paris Cité (CRESS-UMR1153), Inserm/Université Paris Descartes, 1 place du Parvis Notre Dame, Paris 75004, France; Centre d'Épidémiologie Clinique, AP-HP (Assistance Publique des Hôpitaux de Paris), Hôpital Hôtel Dieu, 1 place du Parvis Notre Dame, Paris, France; French Cochrane Center, Paris Descartes University, Sorbonne Paris Cité, Faculté de Médecine, 1 place du Parvis Notre Dame, Paris 75004, France. Electronic address: amelie.yavchitz@aphp.fr.
authors: Amélie
authors: A
authors: Yavchitz
authors: Centre de Recherche Épidémiologie et Statistique Sorbonne Paris Cité (CRESS-UMR1153), Inserm/Université Paris Descartes, 1 place du Parvis Notre Dame, Paris 75004, France; Centre d'Épidémiologie Clinique, AP-HP (Assistance Publique des Hôpitaux de Paris), Hôpital Hôtel Dieu, 1 place du Parvis Notre Dame, Paris, France; French Cochrane Center, Paris Descartes University, Sorbonne Paris Cité, Faculté de Médecine, 1 place du Parvis Notre Dame, Paris 75004, France; Department of Epidemiology, Columbia University Mailman School of Public Health, New York, NY, USA.
authors: Philippe
authors: P
authors: Ravaud
authors: Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
authors: Douglas G
authors: DG
authors: Altman
authors: Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada; School of Epidemiology, Public health and Preventive Medicine, Faculty of Medicine, University of Ottawa, Canada.
authors: David
authors: D
authors: Moher
authors: Nordic Cochrane Centre, Rigshospitalet Department 7811, Copenhagen, Denmark; Research Unit for Evidence-Based Medicine, Odense University Hospital/University of Southern Denmark, Odense, Denmark.
authors: Asbjørn
authors: A
authors: Hrobjartsson
authors: Cochrane Editorial Unit, London, UK.
authors: Toby
authors: T
authors: Lasserson
authors: Centre de Recherche Épidémiologie et Statistique Sorbonne Paris Cité (CRESS-UMR1153), Inserm/Université Paris Descartes, 1 place du Parvis Notre Dame, Paris 75004, France; Centre d'Épidémiologie Clinique, AP-HP (Assistance Publique des Hôpitaux de Paris), Hôpital Hôtel Dieu, 1 place du Parvis Notre Dame, Paris, France; French Cochrane Center, Paris Descartes University, Sorbonne Paris Cité, Faculté de Médecine, 1 place du Parvis Notre Dame, Paris 75004, France.
authors: Isabelle
authors: I
authors: Boutron
mesh_terms: D015340:Epidemiologic Research Design; D019317:Evidence-Based Medicine / Q000379:methods; D006801:Humans; D015201:Meta-Analysis as Topic; D058028:Research Report / Q000592:standards*; D012196:Review Literature as Topic
keywords: Bias; Classification; Data interpretation; Distortion; Spin; Systematic reviews