Cultural adaptation of the Work Disability Functional Assessment Battery (WD-FAB) into German (Germany): hybrid application of two adaptation approaches.

BACKGROUND: The Work Disability Functional Assessment Battery (WD-FAB) was developed based on the International Classification of Functioning, Disability and Health (ICF) framework and administered using a computer adaptive test (CAT) to assess individuals' functional status. The framework and assessment of functional status is especially pertinent in Germany as one factor in determining work disability. This paper reports on the translation and cultural adaptation of the WD-FAB from English (USA) to German (Germany). METHODOLOGY: A combination of forward-backward and dual-panel approaches was used to translate the WD-FAB into German. During the reconciliation process after forward and backward translations, a selection of items was discussed with the forward/backward certified translators, discussed with developers of the WD-FAB and selected for dual-panel discussion. A field test with rehabilitation patients was conducted to finalize the adaptation. RESULTS: 401 unique items from the original WD-FAB and version 3.0 (the majority of the items were the same across versions) were translated into German. After forward translation, the majority of the items were easily reconciled. Some items (identified by YF and TK) could not be easily reconciled and required additional examination. Based on the reasons for difficulties in forward translation, items were selected for the translation panel discussions (n = 69), discussed with developers (n = 49) and/or further discussed with the two forward translators (n = 18). After the first reconciliation and backward translation, 31 items were discussed with all translators again and 4 were again discussed with developers. 77 rehabilitation patients participated in the field test, 29 of whom provided feedback suggesting further revisions. Through the entire adaptation process, the items that were problematic involved those dealing with "anger" and "stress". Furthermore, environmental differences between Germany and the USA limited the adaptation of some physical functioning items. CONCLUSIONS: Despite some differences in the cultural and structural context, we successfully adapted the WD-FAB item banks to German. Future validation of the measure is necessary to understand whether the items have similar psychometric measurement properties to those of the original WD-FAB.