Discrepancies between the Dermatology Life Quality Index and utility scores

Objective: In many jurisdictions, deterioration in quality of life assessed with Dermatology Life Quality Index (DLQI) is used for medical and reimbursement decisions in various dermatological conditions such as psoriasis. However, utility values for health states defined by the DLQI have not yet been evaluated. Therefore, we aim to estimate utilities for different health states described by the ten items of the DLQI.

Methods: A cross-sectional survey was performed in a convenience sample of the general population. Seven DLQI health states with total scores of 6, 11 and 16 (3-3 and 1 states, respectively) were developed. All of them were different from each other in the number of affected items and severity levels of impairment. The 10-year time trade-off method was used to value health states.

Results: Mean utilities elicited by the respondents (n = 308) for the three 6-, three 11- and one 16-point DLQI health states were 0.62-0.75, 0.59-0.66, and 0.56, respectively. In half of the six pairwise comparisons, where health states with the same total DLQI score were compared, significant difference between utilities was found. In eight out of the 15 comparisons between health states with different DLQI scores, utilities were not significantly different.

Conclusions: Utility values for health states with identical DLQI total score may significantly vary. This result might be generalisable to various patient populations, in which the DLQI is used; nevertheless, further research is needed. The discrepancies between DLQI scores and utilities might have an impact on medical and reimbursement decisions as they make the utility gain from treatment uncertain.