title: Evaluating the cross-cultural validity of the Polish version of the Four-Dimensional Symptom Questionnaire (4DSQ) using differential item functioning (DIF) analysis.
abstract: BACKGROUND
  The original Dutch Four-Dimensional Symptom Questionnaire (4DSQ), which measures distress, depression, anxiety and somatization, has been translated into Polish with the aim of providing primary health care with a good screening instrument for the detection of the most prevalent mental health problems (anxiety, somatization, depression and distress).
  
  
  OBJECTIVE
  To check if the Polish version is cross-culturally valid so that the scores of Polish subjects can be compared with the scores of Dutch subjects and the Dutch cut-off points can be used in Polish subjects.
  
  
  METHODS
  4DSQ data were collected from a mixed sample of students and primary care attendees. The Polish data were compared with the 4DSQ data of a matched sample of Dutch students and primary care attendees. Two methods of differential item functioning (DIF) analysis, ordinal logistic regression and generalized Mantel-Haenszel, were used to detect items with DIF, and linear regression analysis was used to estimate the scale-level impact of DIF.
  
  
  RESULTS
  Four items showing DIF were detected in the distress scale, one in the somatization scale and one in the anxiety scale. The DIF in distress caused Polish subjects with moderate scores to score circa 1 point less than their Dutch counterparts.
  
  
  CONCLUSIONS
  The results of the DIF analyses suggest that the Polish 4DSQ measures the same constructs as the Dutch 4DSQ and that the Dutch norms can be used for the Polish subjects, except for distress: the first cut-off point should be one point lower.
authors.affiliation: Family Doctor Department, Medical College, Nicolaus Copernicus University, Torun, Poland. s.czachowski@to.home.pl
authors.forename: Sławomir
authors.initials: S
authors.lastname: Czachowski
authors.forename: Berend
authors.initials: B
authors.lastname: Terluin
authors.forename: Adam
authors.initials: A
authors.lastname: Izdebski
authors.forename: Paweł
authors.initials: P
authors.lastname: Izdebski
mesh_terms: D000328:Adult; D003431:Cross-Cultural Comparison; D005194:Family Practice; D005260:Female; D006801:Humans; D007802:Language; D016015:Logistic Models; D008297:Male; D001523:Mental Disorders / Q000175:diagnosis*; D008875:Middle Aged; D009426:Netherlands; D011044:Poland; D011795:Surveys and Questionnaires / Q000592:standards*