A method to select an instrument for measurement of HR-QOL for cross-cultural adaptation applied to dermatology

Abstract

Objective: The objective of this study was to develop a process to obtain an instrument to measure dermatology specific health-related quality of life (HR-QOL), and to adapt it into another culture, namely the Spanish-speaking community.

Design and setting: By consensus, a multi-disciplinary team determined the qualities of an 'ideal' questionnaire as follows: need (absence of any such instrument), utility, multi-dimensionality, psychometric development, simplicity, high degree of standardisation, and accessibility. A bibliographic search was conducted on Medline, EMBASE and IME (Spanish Medical Index), using 'dermatology' and 'quality of life' as the key words, from January 1990 through to September 1997, supplemented by a second level reference search, to identify the instruments already in existence. Rather than develop a questionnaire ex novo, it was decided to make a cultural adaptation of an existing one. The questionnaires identified in the literature search were classified according to their generic or specific scope and it was decided to adapt a dermatology specific instrument. To select and compare the instruments, a model was developed which would provide an Adaptation Index (ADAPT), which includes the degree of development of psychometric properties, the formal design and the degree of standardisation at a given moment in time.

Results: Six dermatology specific scales were identified: Impact of Skin Disease Scale (IMPACT), Dermatology Life Quality Index (DLQI), Skindex, Dermatology Quality-of-Life Scales (DQOLS), Dermatology Specific Quality of Life (DSQL) and Qualita di Vita Italiana in Dermatologia (QUAVIDERM). The ADAPT Index for each of the above was determined at the time of the study and the DLQI was chosen for adaptation (ADAPT = 77, October 1997).

Conclusions: The study showed the utility of ADAPT Index to assist in the selection process of the questionnaire to adapt. The results of the analysis indicate that in order to introduce and systematically use dermatology specific HR-QOL instruments, the indices require consolidation and improvement. There is a special need for an effort to be made in developing transculturally equivalent instruments suitable for international research.