title: Measuring improvement in depression in cancer patients: a 50% drop on the self-rated SCL-20 compared with a diagnostic interview.
abstract: OBJECTIVE
  To determine the validity of a 50% drop in the 20-item Symptom Checklist Depression Scale (SCL-20) score against the "gold standard" of no longer meeting criteria for major depression as assessed using a diagnostic interview in an outpatient cancer population and also to examine the validity of other potential cut-offs (i.e., percentage drops).
  
  
  METHODS
  Secondary analysis of data from a randomized trial which compared collaborative care with usual care for cancer patients with major depression. A total of 194 trial participants who had both SCL-20 scores and depression diagnoses on the Structured Clinical Interview for DSM-IV at both baseline and at 12-week outcome formed the analyzed sample.
  
  
  RESULTS
  A 50% reduction in the SCL-20 score from baseline to 12 weeks correctly identified the patients who no longer met criteria for major depression in 153 (78.9%) of 194 (95% CI 73.1% to 84.6%) cases. Most of those misclassified had not achieved a 50% reduction in SCL-20 score despite no longer meeting criteria for major depression. Examination of the performance of percentage drops other than 50% on the SCL-20 using a receiver operating characteristics (ROC) curve and histogram of misclassification suggested that the 50% drop was best if both a low overall misclassification rate and the minimizing of false positives of improvement were required.
  
  
  CONCLUSIONS
  A 50% reduction in the SCL-20 score performs well as a conservative measure of change in depression status in cancer patients.
authors.affiliation: Psychological Medicine Research, University of Edinburgh Cancer Research Centre, School of Molecular and Clinical Medicine, University of Edinburgh, Edinburgh EH4 2XR, Scotland, UK. m.oconnor@doctors.org.uk
authors.forename: Mark
authors.initials: M
authors.lastname: O'Connor
authors.forename: Isabella
authors.initials: I
authors.lastname: Butcher
authors.forename: Christian Holm
authors.initials: CH
authors.lastname: Hansen
authors.forename: Annet
authors.initials: A
authors.lastname: Kleiboer
authors.forename: Gordon
authors.initials: G
authors.lastname: Murray
authors.forename: Neelom
authors.initials: N
authors.lastname: Sharma
authors.forename: Parvez
authors.initials: P
authors.lastname: Thekkumpurath
authors.forename: Jane
authors.initials: J
authors.lastname: Walker
authors.forename: Michael
authors.initials: M
authors.lastname: Sharpe
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D057189:Checklist / Q000295:instrumentation*; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000523:psychology*; D017063:Outcome Assessment, Health Care / Q000379:methods*; D010361:Patients / Q000523:psychology*; D012372:ROC Curve; D006113:United Kingdom; D055815:Young Adult