Is the DLQI appropriate for medical decision-making in psoriasis patients?

Dermatology Life Quality Index (DLQI) is the most commonly applied measure of health-related quality of life (HRQoL) in psoriasis patients. It is among defining criteria of moderate-to-severe psoriasis and present in treatment guidelines. Our objective was to estimate preference-based HRQoL values (i.e., utilities) for hypothetical health states described by the 10 items of the DLQI in psoriasis patients. Moreover, we compare results to findings of a similar study previously conducted among the general public. A cross-sectional survey was carried out among 238 psoriasis patients. Seven hypothetical DLQI-defined health states with total scores of 6, 11, and 16 (3–3 and 1 states, respectively) were evaluated by time trade-off method. The difference in DLQI scores between hypothetical health states was set at 5 points, as it exceeds the minimal clinically important difference (MCID). Utility scores were found to be homogenous across the seven hypothetical health states (range of means for the 6-point states 0.85–0.91, range of means for the 11-point states 0.83–0.85, and mean of 0.84 for the 16-point state). Overall, mean utilities assessed by psoriasis patients were higher for all seven states compared with the general public (mean difference 0.16–0.28; p < 0.001). In 11 out of the 15 comparisons between health states with DLQI scores differing larger than the MCID, there was no statistically significant difference in utility. Thus, in clinical settings, patients with DLQI scores differing more than the MCID may have identical HRQoL. Improving the definition of moderate-to-severe disease and reconsideration of the DLQI in clinical assessment of psoriasis patients are suggested.