title: Cross-language measurement equivalence of the Center for Epidemiologic Studies Depression (CES-D) scale in systemic sclerosis: a comparison of Canadian and Dutch patients.
abstract: OBJECTIVE
  Increasingly, medical research involves patients who complete outcomes in different languages. This occurs in countries with more than one common language, such as Canada (French/English) or the United States (Spanish/English), as well as in international multi-centre collaborations, which are utilized frequently in rare diseases such as systemic sclerosis (SSc). In order to pool or compare outcomes, instruments should be measurement equivalent (invariant) across cultural or linguistic groups. This study provides an example of how to assess cross-language measurement equivalence by comparing the Center for Epidemiologic Studies Depression (CES-D) scale between English-speaking Canadian and Dutch SSc patients.
  
  
  METHODS
  The CES-D was completed by 922 English-speaking Canadian and 213 Dutch SSc patients. Confirmatory factor analysis (CFA) was used to assess the factor structure in both samples. The Multiple-Indicator Multiple-Cause (MIMIC) model was utilized to assess the amount of differential item functioning (DIF).
  
  
  RESULTS
  A two-factor model (positive and negative affect) showed excellent fit in both samples. Statistically significant, but small-magnitude, DIF was found for 3 of 20 items on the CES-D. The English-speaking Canadian sample endorsed more feeling-related symptoms, whereas the Dutch sample endorsed more somatic/retarded activity symptoms. The overall estimate in depression scores between English and Dutch was not influenced substantively by DIF.
  
  
  CONCLUSIONS
  CES-D scores from English-speaking Canadian and Dutch SSc patients can be compared and pooled without concern that measurement differences may substantively influence results. The importance of assessing cross-language measurement equivalence in rheumatology studies prior to pooling outcomes obtained in different languages should be emphasized.
authors: Department of Rheumatology, Sint Maartenskliniek Nijmegen, The Netherlands. kwakkenbosL@gmail.com
authors: Linda
authors: L
authors: Kwakkenbos
authors: Erin
authors: E
authors: Arthurs
authors: Frank H J
authors: FH
authors: van den Hoogen
authors: Marie
authors: M
authors: Hudson
authors: Wim G J M
authors: WG
authors: van Lankveld
authors: Murray
authors: M
authors: Baron
authors: Cornelia H M
authors: CH
authors: van den Ende
authors: Brett D
authors: BD
authors: Thombs
mesh_terms: D000328:Adult; D000368:Aged; D002170:Canada / Q000453:epidemiology; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D011569:Psychiatric Status Rating Scales; D012595:Scleroderma, Systemic / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D014481:United States / Q000453:epidemiology; D044465:White People