title: Effects of drop-out on efficacy estimates in five Cochrane reviews of popular antipsychotics for schizophrenia.
abstract: OBJECTIVE
  Our aim was to find out how Cochrane reviews of five popular or frequently prescribed second-generation antipsychotics in the UK (olanzapine, risperidone, quetiapine, amisulpride and aripiprazole) approached the problem of high drop-out in placebo-controlled trials.
  
  
  METHODS
  We examined the following: (i) whether reviews included data from studies with a level of drop-out exceeding their stated exclusion criterion; (ii) the level of missing data each efficacy outcome in each review relied upon; and (iii) impact of excluding studies with high drop-out.
  
  
  RESULTS
  All reviews included data they stated they would exclude because of unacceptable levels of attrition, four (risperidone, olanzapine, amisulpride, aripiprazole) without clear acknowledgement or justification. Several reviews also excluded data from a number of relatively low-attrition studies because of missing standard deviations.
  
  
  CONCLUSIONS
  Cochrane reviews of five popular antipsychotics for schizophrenia misrepresented the available evidence on their efficacy. The impact of including high-attrition studies was difficult to quantify because of the exclusion of relevant low-attrition studies. Further analysis of the efficacy of these drugs in studies with acceptable rates of attrition is required. To reduce the problem of high attrition, trialists should gather follow-up data from people who leave the double-blind process early.
authors.affiliation: Greater Manchester West Mental Health Foundation NHS Trust, UK. paulhutton@nhs.net
authors.forename: P
authors.initials: P
authors.lastname: Hutton
authors.forename: A P
authors.initials: AP
authors.lastname: Morrison
authors.forename: A R
authors.initials: AR
authors.lastname: Yung
authors.forename: P J
authors.initials: PJ
authors.lastname: Taylor
authors.forename: P
authors.initials: P
authors.lastname: French
authors.forename: G
authors.initials: G
authors.lastname: Dunn
mesh_terms: D000077582:Amisulpride; D014150:Antipsychotic Agents / Q000627:therapeutic use*; D000068180:Aripiprazole; D001569:Benzodiazepines / Q000627:therapeutic use; D003627:Data Interpretation, Statistical; D003987:Dibenzothiazepines / Q000627:therapeutic use; D006801:Humans; D000077152:Olanzapine; D010352:Patient Dropouts / Q000706:statistics & numerical data*; D010879:Piperazines / Q000627:therapeutic use; D000069348:Quetiapine Fumarate; D015363:Quinolones / Q000627:therapeutic use; D012196:Review Literature as Topic; D018967:Risperidone / Q000627:therapeutic use; D012559:Schizophrenia / Q000188:drug therapy*; D013469:Sulpiride / Q000031:analogs & derivatives / Q000627:therapeutic use
chemical_list: D014150:Antipsychotic Agents; D003987:Dibenzothiazepines; D010879:Piperazines; D015363:Quinolones; D001569:Benzodiazepines; D000069348:Quetiapine Fumarate; D013469:Sulpiride; D000077582:Amisulpride; D000068180:Aripiprazole; D018967:Risperidone; D000077152:Olanzapine