The Validity and Reliability of the Dermatology Life Quality Index (DLQI) in Thais

Abstract

The Dermatology Life Quality Index (DLQI) is a simple and validated 10-item English language-questionnaire designed to measure and compare disability resulting from dermatological conditions. It has been adapted into many languages. The purpose of this study is to evaluate the validity of the Thai version of the DLQI by measuring and comparing disability resulting from a variety of common dermatological conditions. In order to assess its validity, the Thai version of the DLQI was completed by 200 first-time patients attending the dermatology clinic, Siriraj Hospital, Mahidol University and the results were compared to those of 100 healthy volunteers. In order to assess its reliability, the completed DLQI questionnaires from 50 patients using a 1 week

test-retest method were analyzed. Patients took between 1 and 5 minutes to complete the Thai version DLQI questionaire. The mean overall DLQI score of the 200 patients in this study was 9.8(SD 6.9), and for volunteers in the control group was 0.7(SD 1.2). The scores of the patients with urticaria, psoriasis, eczema, acne, vitiligo, fungal infection and melasma were significantly higher than those of the control group (p<0.0001), indicating high validity of the DLQI Thai version. The scores of the patients with urticaria, psoriasis, eczema, acne, vitiligo fungal infection and melasma were also significantly higher than those of patients with viral wart, seborrheic keratosis, moles and benign skin tumors. Test-retest reliability were assessed using weighted "kappa (Kw) score" for each question . The Kw ranged from 0.70 to 0.86 which indicated good agreement. For total score, the intraclass correlation coefficient (r1) was 0.96 (95% CI = 0.92, 0.98) which indicated good reliability. The Thai version of the DLQI has high validity and good reliability. It is a useful easily and rapidly administered instrument for measuring the QOL for patients with various skin diseases in Thais.