title: Rasch analysis supports the use of the depression, anxiety, and stress scales to measure mood in groups but not in individuals with chronic low back pain.
abstract: OBJECTIVE
  Chronic pain is a common problem that is associated with mood disorders such as depression. The Depression, Anxiety, and Stress Scales (DASS-21) questionnaire is commonly used to help measure disordered mood. In this study, we used Rasch analysis to analyze the clinimetric properties of the DASS-21 in a chronic low back pain sample.
  
  
  METHODS
  A Rasch analysis was conducted on data collected as a part of a randomized hospital-based placebo-controlled trial. DASS-21 questionnaires were completed by the 154 enrolled participants.
  
  
  RESULTS
  The DASS-21 subscales fit the Rasch model. No differential item functioning was detected for age, gender, pain severity, or disability. Reliability for individual use was supported for the depression subscale (Person Separation Index [PSI]=0.86) but group use only for the anxiety (PSI=0.74) and stress (PSI=0.82) subscales. A DASS-21 aggregate score of "negative affect" lacked fit to the Rasch model (χ(2)=191.48, P<0.001).
  
  
  CONCLUSIONS
  This is the first study that used Rasch analysis to demonstrate that the DASS-21 subscales demonstrate adequate measurement properties for research involving groups with chronic pain. Only the DASS-21 depression subscale demonstrated adequate reliability for use with individuals with chronic pain. The use of a single DASS-21 aggregate score as a measure of "negative affect" was not supported.
authors: Neuroscience Research Australia, University of New South Wales, PO Box 1165, Randwick, NSW 2031, Australia. L.Parkitny@neura.edu.au
authors: Luke
authors: L
authors: Parkitny
authors: James Henry
authors: JH
authors: McAuley
authors: David
authors: D
authors: Walton
authors: Leonardo Oliveira
authors: LO
authors: Pena Costa
authors: Kathryn M
authors: KM
authors: Refshauge
authors: Benedict Martin
authors: BM
authors: Wand
authors: Flavia
authors: F
authors: Di Pietro
authors: G Lorimer
authors: GL
authors: Moseley
mesh_terms: D000339:Affect; D001007:Anxiety / Q000175:diagnosis*; D002908:Chronic Disease; D003863:Depression / Q000175:diagnosis*; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D013315:Stress, Psychological / Q000175:diagnosis*; D011795:Surveys and Questionnaires