BACKGROUND: The Patient-Reported Outcome Measurement Information System (PROMIS) is an assessment system that aims to provide more valid, reliable, responsive, and precise patient-reported outcome (PRO) measures than has been previously available. This paper documents the translation of the Physical Function item bank into Danish.

METHODS: We followed the PROMIS standard procedure, including: 1) two independent translations, 2) back translation, 3) independent reviews of translation quality, and 4) cognitive interviews with a representative sample of the adult population from the municipality of Copenhagen. After each phase, the new information was reviewed and the Danish version of the PROMIS Physical Function items was revised, if warranted.

RESULTS: Relatively few problems were related to translation in itself and such problems could be fixed by changes in item wordings to fit the Danish context. Cognitive testing revealed problem of a general issue: annoyance in case of mismatch between respondents' functional level and question difficulty, problems imagining performance on activities that the respondents did not usually do, and uncertainty whether mobility aids (e.g., canes and walkers) should be considered when performing an activity. Solutions to the more general issues would require revisions to the original items.

CONCLUSIONS: The standard translation methodology was successful in eliminating problems in translation, and pointed to problems of a general issue in some of the original questions, producing translated Danish versions of the PROMIS Physical Functioning items. Translation and validation studies provide a valuable source when revising and improving PROs in a clinical setting or for research. The present paper exemplifies this with experiences from Denmark. The study describes how the use of PROs when measuring physical functioning in a Danish context can be improved-hence improving the items used for research, future trials and in clinical settings.