The Dermatology Life Quality Index 1994-2007: a comprehensive review of validation data and clinical results

Background The Dermatology Life Quality Index (DLQI) is one of the most widely used dermatology-specific quality of life instruments. Over the last 5 years there has been great interest in its use. Objectives To collect and present all information regarding the technical properties and the clinical use of the DLQI from the date it was published to the end of 2007 for use as a single source of reference. Methods A detailed literature search was conducted using electronic reference databases and the DLQI library in the Department of Dermatology, Cardiff University. All publications mentioning any aspect of the DLQI, from the time of its development to the end of 2007, were identified and the data concerning the DLQI in terms of its psychometric analysis, and use in clinical trials, epidemiological studies and health services research, were extracted and tabulated with all the relevant references. Results In total, 272 full articles which have included the DLQI were reviewed. Studies described in these articles were divided into five main categories: psychometric studies, descriptive/epidemiological studies, drug (topical and systemic) trials, clinical practice research, and therapeutic interventions. The DLQI has been used in 33 different skin conditions in 32 countries and is available in 55 languages. Psychometric aspects of the DLQI such as validity, reliability, responsiveness to change, factor structure, and minimal important difference were described in 115 studies. The DLQI has been used in 33 studies assessing the effectiveness of 14 different types of therapeutic interventions and in 37 studies evaluating nine types of clinical practice research. Sixty studies have used it alone or in parallel with other instruments as an outcome measure in clinical trials of 18 systemic drugs while 22 studies have used it in 14 different topical drug trials. The DLQI has also been used in 27 multinational studies. Conclusions During the last 14 years there has been a gradual increase in the international use of the DLQI. The brevity and simplicity of use of the DLQI has resulted in its popularity both in clinical practice and in research. However, there are various issues in particular regarding its unidimensionality, differential item functioning, and minimal clinically important difference, which require further research. This article should facilitate the work of potential users of the DLQI by providing a readily available source of references for different aspects of the DLQI.