title: Language-related differential item functioning between English and German PROMIS Depression items is negligible.
abstract: To investigate differential item functioning (DIF) of PROMIS Depression items between US and German samples we compared data from the US PROMIS calibration sample (n = 780), a German general population survey (n = 2,500) and a German clinical sample (n = 621). DIF was assessed in an ordinal logistic regression framework, with 0.02 as criterion for R2-change and 0.096 for Raju's non-compensatory DIF. Item parameters were initially fixed to the PROMIS Depression metric; we used plausible values to account for uncertainty in depression estimates. Only four items showed DIF. Accounting for DIF led to negligible effects for the full item bank as well as a post hoc simulated computer-adaptive test (< 0.1 point on the PROMIS metric [mean = 50, standard deviation =10]), while the effect on the short forms was small (< 1 point). The mean depression severity (43.6) in the German general population sample was considerably lower compared to the US reference value of 50. Overall, we found little evidence for language DIF between US and German samples, which could be addressed by either replacing the DIF items by items not showing DIF or by scoring the short form in German samples with the corrected item parameters reported.
authors.affiliation: Department of Psychosomatic Medicine, Clinic for Internal Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.|Institute for Social Medicine, Epidemiology and Health Economics, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: H Felix
authors.initials: HF
authors.lastname: Fischer
authors.affiliation: Department of Psychosomatic Medicine and Psychotherapy, University Medical Center Hamburg-Eppendorf & Schön Klinik Hamburg Eilbek, Hamburg, Germany.
authors.forename: Inka
authors.initials: I
authors.lastname: Wahl
authors.affiliation: Department of Psychosomatic Medicine, Clinic for Internal Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.|Population Health Strategic Research Centre, School of Health and Social Development, Deakin University, Melbourne, Victoria, Australia.
authors.forename: Sandra
authors.identifier: 0000-0001-6185-9423
authors.initials: S
authors.lastname: Nolte
authors.affiliation: Department of Psychosomatic Medicine, Clinic for Internal Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Liegl
authors.affiliation: Department of Medical Psychology and Medical Sociology, University of Leipzig, Leipzig, Germany.|Klinik und Poliklinik für Psychosomatische Medizin und Psychotherapie, Universitätsmedizin Mainz, Mainz, Germany.
authors.forename: Elmar
authors.initials: E
authors.lastname: Brähler
authors.affiliation: Department of Psychosomatic Medicine and Psychotherapy, University Medical Center Hamburg-Eppendorf & Schön Klinik Hamburg Eilbek, Hamburg, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Löwe
authors.affiliation: Department of Psychosomatic Medicine, Clinic for Internal Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.|Department of Quantitative Health Sciences, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: Matthias
authors.initials: M
authors.lastname: Rose
mesh_terms: D000328:Adult; D000368:Aged; D003863:Depression / Q000175:diagnosis*; D003866:Depressive Disorder / Q000175:diagnosis*; D005260:Female; D005858:Germany; D006801:Humans; D008297:Male; D008875:Middle Aged; D000071066:Patient Reported Outcome Measures; D011594:Psychometrics / Q000592:standards*; D014481:United States
keywords: Item-Response Theory; PROMIS; depression; differential item functioning; outcome assessment; patient-reported outcomes