title: Variability in depression prevalence in early rheumatoid arthritis: a comparison of the CES-D and HAD-D Scales.
abstract: BACKGROUND
  Depression is common in rheumatoid arthritis (RA), however reported prevalence varies considerably. Two frequently used instruments to identify depression are the Center for Epidemiological Studies Depression (CES-D) scale, and the Hospital Anxiety and Depression Scale (HADS). The objectives of this study were to test if the CES-D and HADS-D (a) satisfy current modern psychometric standards for unidimensional measurement in an early RA sample; (b) measure the same construct (i.e. depression); and (c) identify similar levels of depression.
  
  
  METHODS
  Data from the two scales completed by patients with early RA were fitted to the Rasch measurement model to show that (a) each scale satisfies the criteria of fit to the model, including strict unidimensionality; (b) that the scales can be co-calibrated onto a single underlying continuum of depression and to (c) examine the location of the cut points on the underlying continuum as indication of the prevalence of depression.
  
  
  RESULTS
  Ninety-two patients with early RA (62% female; mean age = 56.3, SD = 13.7) gave 141 sets of paired CES-D and HAD-D data. Fit of the data from the CES-D was found to be poor, and the scale had to be reduced to 13 items to satisfy Rasch measurement criteria whereas the HADS-D met model expectations from the outset. The 20 items combined (CES-D13 and HADS-D) satisfied Rasch model expectations. The CES-D gave a much higher prevalence of depression than the HADS-D.
  
  
  CONCLUSIONS
  The CES-D in its present form is unsuitable for use in patients with early RA, and needs to be reduced to a 13-item scale. The HADS-D is valid for early RA and the two scales measure the same underlying construct but their cut points lead to different estimates of the level of depression. Revised cut points on the CES-D13 provide comparative prevalence rates.
authors.affiliation: School of Psychology, University of Western Sydney, Penrith South DC 1797, NSW, Australia. t.covic@uws.edu.au
authors.forename: Tanya
authors.initials: T
authors.lastname: Covic
authors.forename: Julie F
authors.initials: JF
authors.lastname: Pallant
authors.forename: Alan
authors.initials: A
authors.lastname: Tennant
authors.forename: Sally
authors.initials: S
authors.lastname: Cox
authors.forename: Paul
authors.initials: P
authors.lastname: Emery
authors.forename: Philip G
authors.initials: PG
authors.lastname: Conaghan
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000453:epidemiology* / Q000523:psychology*; D016477:Artifacts; D003866:Depressive Disorder / Q000453:epidemiology*; D004185:Disability Evaluation; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009483:Neuropsychological Tests / Q000592:standards / Q000706:statistics & numerical data*; D011237:Predictive Value of Tests; D015995:Prevalence; D015203:Reproducibility of Results