title: Shortening the PHQ-9: a proof-of-principle study of utilizing Stochastic Curtailment as a method for constructing ultrashort screening instruments.
abstract: OBJECTIVE
  In primary care, screening instruments for mental health should be ultrashort to allow for routine usage. In this paper, Stochastic Curtailment is introduced as a method for constructing ultrashort screeners.
  
  
  METHODS
  In a post hoc diagnostic accuracy study using the item scores on the Patient Health Questionnaire depression module (PHQ-9) of a large sample (N=20, 685), Stochastic Curtailment was compared with two existing ultrashort versions of PHQ-9. The first was PHQ-2 (which includes the first two items of PHQ-9), and the second was a 'two-step' method (only if the PHQ-2 screened positive were all nine PHQ items administered). For PHQ-2 and two-step, both cut scores 2 and 3 were evaluated.
  
  
  RESULTS
  PHQ-2 showed the lowest and Stochastic Curtailment the highest diagnostic accuracy with reference to the classifications based on the full PHQ-9. To do so, Stochastic Curtailment used 3.08 items on average (S.D.=1.98), which was slightly less than two-step (M=3.18, S.D.=2.62) under its most accurate cut score (≥2).
  
  
  CONCLUSIONS
  It was concluded that Stochastic Curtailment is a promising method for constructing ultrashort screeners.
authors.affiliation: Department of Clinical Psychology and Department of Methods, Faculty of Psychology and Education, VU University, Amsterdam, the Netherlands. Electronic address: n.smits@vu.nl.
authors.forename: Niels
authors.initials: N
authors.lastname: Smits
authors.affiliation: Tufts Clinical and Translational Science Institute, Tufts University and Institute for Clinical Research and Health Policy Studies, Tufts Medical Center, Boston, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Finkelman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003863:Depression / Q000175:diagnosis; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D011320:Primary Health Care; D011594:Psychometrics / Q000295:instrumentation*; D013269:Stochastic Processes; D011795:Surveys and Questionnaires / Q000592:standards*; D055815:Young Adult
keywords: Curtailment; Mental health; Respondent burden; Screening