title: Utility of an effect size analysis for communicating treatment effectiveness: a case study of cholinesterase inhibitors for Alzheimer's disease.
abstract: OBJECTIVE
  To highlight the utility of using an effect size analysis to communicate the effectiveness of treatment interventions.
  
  
  METHODS
  Secondary analysis.
  
  
  METHODS
  Previously published systematic review on cholinesterase inhibitors (ChEIs) in Alzheimer's disease.
  
  
  METHODS
  Individuals with mild to moderate Alzheimer's disease.
  
  
  METHODS
  Six-month randomized controlled trials involving a placebo group and a ChEI group (donepezil, galantamine, or rivastigmine).
  
  
  METHODS
  Cognitive function was assessed according to performance on the cognition subscale of the Alzheimer's Disease Assessment Scale (ADAS-Cog). Global Function was quantified using the Clinician's Interview-Based Impression of Change-Plus (CIBIC-Plus). Harm was defined as withdrawal from a trial because of an adverse event. Several effect size indices were computed based on these domains: the success rate difference (SRD), the harm rate difference (HRD), the number needed to treat (NNT) or harm (NNH), and the area under the curve (AUC). Harm:benefit ratios were also computed to compare effect size indices across domains of function.
  
  
  RESULTS
  In terms of benefit, the NNT for cognition ranged from 4 to 14 (corresponding AUC values: 0.64-0.54), and the NNT for global function ranged from 6 to 100 (corresponding AUC 0.59-0.51). In terms of harm, the NNH ranged from 6 to 20 (corresponding AUC 0.58-0.53). Only one of the four studies had favorable harm:benefit ratios in both the cognition and global function domains.
  
  
  CONCLUSIONS
  Effect size indices should be reported in clinical trials because they provide important insight into the clinical meaningfulness of results. Additional benefit is gained by comparing effect size indices across domains of function to reveal harm:benefit ratios.
authors.affiliation: Department of Psychology, Trent University, Peterborough, Ontario, Canada. kevinpeters@trentu.ca
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Peters
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000188:drug therapy; D019540:Area Under Curve; D002800:Cholinesterase Inhibitors / Q000009:adverse effects / Q000627:therapeutic use*; D000077265:Donepezil; D005702:Galantamine / Q000009:adverse effects / Q000627:therapeutic use; D006801:Humans; D007189:Indans / Q000009:adverse effects / Q000627:therapeutic use; D048448:Phenylcarbamates / Q000009:adverse effects / Q000627:therapeutic use; D010880:Piperidines / Q000009:adverse effects / Q000627:therapeutic use; D016032:Randomized Controlled Trials as Topic; D000068836:Rivastigmine; D016896:Treatment Outcome
chemical_list: D002800:Cholinesterase Inhibitors; D007189:Indans; D048448:Phenylcarbamates; D010880:Piperidines; D005702:Galantamine; D000077265:Donepezil; D000068836:Rivastigmine
keywords: clinical meaningfulness; dementia; treatment