The Dermatitis Family Impact questionnaire: a review of its measurement properties and clinical application.

The Dermatitis Family Impact (DFI) questionnaire is a disease-specific measure to assess the impact of atopic eczema on the quality of life (QoL) of the parents and family members of affected children. We set out to review the published literature and to collate data on the clinical and psychometric aspects of the DFI questionnaire from its development in 1998-2012, in order to create a single source of reference for users of the DFI. A literature search was performed of publications, including abstracts, describing the use of the DFI between 1998 and 2012. In total, we identified 53 publications (37 full articles and 16 abstracts) describing the use of the DFI in 50 studies. Only one study demonstrated test-retest reliability (r = 0 . 95). Three studies demonstrated internal consistency, with Cronbach α ranging from 0.85 to 0.90. Fifteen studies showed sensitivity to change of DFI scores, with significant differences between baseline and the end of the study. Twenty-six studies correlated the DFI to other objective and subjective instruments to demonstrate its construct (convergent) validity. Seventeen validated translations of the DFI have been used in 16 different countries (including two multinational studies). Nine clinical studies have assessed the effectiveness of five different topical drugs and one probiotic supplement. Two studies have assessed the effectiveness of care by dermatology nurses and dermatologists. The use of the DFI has revealed the major impact of atopic eczema on the QoL of families of affected children. The strengths of the DFI include wide international experience of its use, defined test-retest reliability, good internal consistency, sensitivity to change, and good construct (convergent) validity. Areas requiring further research include creation of validated score descriptors, assessment of minimum important clinical difference and testing of dimensionality, factor structure and differential item functioning.