Cross validation of the Turkish version of dermatology life quality index

Abstract

Background: The aim of this study was to test the linguistic validation of the Turkish version of the Dermatology Life Quality Index (DLQI) for Turkish speaking dermatology patients.

Methods: The DLQI is a 10-item dermatology specific index developed originally in English. The methodology of this study consists of four consecutive sections: Translation, cognitive debriefing, field testing and statistical analysis. Translation steps: (a) Two forward independent translations into Turkish, (b) reconciliation of these translations by a dermatologist, (c) backward translation of the consensus Turkish version by a bilingual person into its original language (English), (d) and comparing the original questionnaire with the backward translated one. Cognitive debriefing: Sessions were performed on five patients from each of the seven different dermatological diagnosis groups. Field testing: The final Turkish version on which the face validity was approved by specialists on a total of 79 inpatients/outpatients with various dermatological diagnoses treated at Celal Bayar University Hospital.

Statistical analysis: Internal consistency (using Cronbach a) and item-total score correlations (Pearson correlation) were used for reliability analysis. Validity analysis was carried out by construct testing (principal components factor analysis), convergent (Pearson correlation) and (discriminate Student's t-test and Mann-Whitney U-test) validity, and SF-36 was used in parallel with DLQI in order to test convergent validity. The data were analyzed by the SPSS version 10.0 (SPSS Inc., Chicago, IL, USA) statistical package.

Results: The mean age of the patients in the study was 30.77+/-15.91 years; the mean score of DLQI was 7.61+/-6.12. The median of item-total correlation coefficient was found to be 0.66, within a range of 0.48-0.81. The internal consistency of the index was found to be highly sufficient (alpha=0.85). The DLQI was found to be highly related to the physical domain of SF-36. Life quality score was found to be significantly low for the inpatients compared with outpatients (differential validity).

Conclusion: It was found that the Turkish version of the DLQI was an acceptable index for dermatologists and dermatology patients and, moreover, to be valid and reliable in a cross-sectional level. The responsiveness of the Turkish version of the DLQI needs to be tested further on a variety of dermatological conditions with different severities.