title: How does the threshold score to enter a major depression trial influence the size of the available patient population for study?
abstract: BACKGROUND
  This paper describes the relationship between entry criteria and eligible population for inclusion in Major Depression (MD) clinical trials. Inclusion criteria for a MD study typically require patients to pass a threshold score on a depression rating scale, most commonly the HAM-D or MADRS. A Score To Enter (STE) of > or = 17 on the HAM-D 17-item scale is a typical value, although higher values (i.e. > or = 22 or even > or = 25 points) are often used. It is commonly supposed that patients with higher baseline scores form a more sensitive sample for discriminating active drug from placebo.
  
  
  METHODS
  We present data from a sample of depressed hospital outpatients and describe their general characteristics. We then introduce a model, based upon this sample, which predicts the impact of STE on eligible trial population.
  
  
  CONCLUSIONS
  A small increase in STE has a marked effect on eligible population: an increase in HAM-D (17 item) STE from 17 to 21 and 25 reduces the eligible population by 42 and 76%, respectively. These predictions are reasonably robust when our model is validated with known clinical trial data.
  
  
  CONCLUSIONS
  Our findings have major implications for planning and managing Major Depression trials as higher STEs substantially restrict the proportion of patient eligible for study.
authors.affiliation: Department of Psychiatry, QEII Hospital, Welwyn Garden City, UK. c.l.hawley@herts.ac.uk
authors.forename: C J
authors.initials: CJ
authors.lastname: Hawley
authors.forename: T M
authors.initials: TM
authors.lastname: Gale
authors.forename: T
authors.initials: T
authors.lastname: Sivakumaran
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002986:Clinical Trials as Topic; D015331:Cohort Studies; D003866:Depressive Disorder / Q000523:psychology* / Q000628:therapy*; D004608:Eligibility Determination; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D012107:Research Design; D018401:Sample Size; D012720:Severity of Illness Index