Validity and reliability of the German translation of the Diabetes Foot Self-Care Behavior Scale (DFSBS-D)

Introduction Comprehensive regular foot self-care is one of the most critical self-management behaviors for people with diabetes to prevent foot ulcer development and related complications. Yet, adequate foot self-care is only practiced by very few of those affected. To improve diabetic foot syndrome prevention, a valid and reliable instrument for measuring daily foot-care routines in patients with diabetes is needed. However, no such instrument is currently available in the German language. This study, therefore, aims to translate and cross-culturally adapt the "Diabetic Foot Self-Care Behavior Scale" (DFSBS) into German (DFSBS-D) and evaluate its validity and reliability. Material and methods The DFSBS was translated from English into German using a forward-backward procedure as per previous recommendations. Factor analysis was used to study structural validity. To establish construct validity, 21 a priori hypotheses were defined regarding the expected correlation between scores on the new German version (i.e., DFSBS-D) and those of the following questionnaires measuring related constructs: (1) German version "Diabetes SelfCare Activities Measure" (SDSCA-G), (2) "Frankfurter Catalogue of Foot Self-Care" (FCFSP), and (3) "Short Form 36" (SF-36) and tested in 82 patients. To assess test-retest reliability, patients completed the DFSBS-D again after a 2-week interval. Test-retest reliability was assessed from stable patients' data (n = 48) by calculating two-way randomeffects absolute agreement ICCs with 95% CI and Bland and Altman analyses. In addition, Cronbach's alpha was calculated as internal consistency measure. Results The 7-item DFSBS-D showed good structural validity. Its single factor explains 57% of the total sample variance. Of the 21 predefined hypotheses, 13 (62%) were confirmed. The DFSBS-D's internal consistency was good (Cronbach's alpha = 0.87). Test-retest reliability over a 2-week interval was also good (ICC 0.76). Conclusion The DFSBS was successfully translated into German. Statistical analyses showed good DFSBS-D structural validity, test-retest reliability, and internal consistency. Yet, construct validity may be debated.