title: Simultaneous synthesis of treatment effects and mapping to a common scale: an alternative to standardisation.
abstract: OBJECTIVE
  Trials often may report several similar outcomes measured on different test instruments. We explored a method for synthesising treatment effect information both within and between trials and for reporting treatment effects on a common scale as an alternative to standardisation
  
  
  METHODS
  We applied a procedure that simultaneously estimates a pooled treatment effect and the "mapping" ratios between the treatment effects on test instruments in a connected network. Standardised and non-standardised treatment effects were compared. The methods were illustrated in a dataset of 22 trials of selective serotonin reuptake inhibitors against placebo for social anxiety disorder, each reporting treatment effects on between one and six of a total nine test instruments.
  
  
  RESULTS
  Ratios of treatment effects on different test instruments varied from trial to trial, with a coefficient of variation of 18% (95% credible interval 11-29%). Standardised effect models fitted the data less well, and standardised treatment effects were estimated with less relative precision than non-standardised effects and with greater relative heterogeneity.
  
  
  CONCLUSIONS
  Simultaneous synthesis of treatment effects and mapping to a common scale make fewer assumptions than standardising by dividing effects by the sample standard deviation, allow results to be reported on a common scale, and deliver estimates with superior relative precision.
authors.affiliation: School of Social and Community Medicine, University of Bristol, 39 Whatley Road, Bristol, BS8 2PS, UK.
authors.forename: A E
authors.initials: AE
authors.lastname: Ades
authors.affiliation: School of Social and Community Medicine, University of Bristol, 39 Whatley Road, Bristol, BS8 2PS, UK.
authors.forename: Guobing
authors.initials: G
authors.lastname: Lu
authors.affiliation: School of Social and Community Medicine, University of Bristol, 39 Whatley Road, Bristol, BS8 2PS, UK.
authors.forename: Sofia
authors.initials: S
authors.lastname: Dias
authors.affiliation: Centre for Outcomes Research and Effectiveness, Research Department of Clinical, Educational and Health Psychology, University College London, 1-19 Torrington Place, London, WC1E 7HB, UK.
authors.forename: Evan
authors.initials: E
authors.lastname: Mayo-Wilson
authors.affiliation: School of Social and Community Medicine, University of Bristol, 39 Whatley Road, Bristol, BS8 2PS, UK.
authors.forename: Daphne
authors.initials: D
authors.lastname: Kounali
mesh_terms: D001008:Anxiety Disorders / Q000188:drug therapy; D056808:Biostatistics / Q000379:methods*; D002986:Clinical Trials as Topic / Q000592:standards / Q000706:statistics & numerical data; D016208:Databases, Factual / Q000706:statistics & numerical data; D006801:Humans; D015201:Meta-Analysis as Topic; D017367:Selective Serotonin Reuptake Inhibitors / Q000627:therapeutic use; D012920:Social Behavior Disorders / Q000188:drug therapy; D016896:Treatment Outcome
chemical_list: D017367:Selective Serotonin Reuptake Inhibitors
keywords: evidence synthesis; mapping; multiple outcomes; social anxiety