Health state utility, willingness to pay, and quality of life among Taiwanese patients with psoriasis

Background/Objective: Past studies have found a correlation between the Dermatology Life Quality Index (DLQI) and the Psoriasis Area and Severity Index (PASI) for Caucasian psoriasis patients. This study examined the relationships between health state utility and willingness to pay (WTP) and the DLQI, as well as between the PASI and the DLQI, health-related utilities, and WTP in Taiwanese patients. Methods: A total of 480 psoriasis patients from five hospitals across Taiwan were interviewed between August 2009 and February 2010. Health state utilities were elicited using the time trade-off (TTO) method, a visual analog scale (VAS), and the EuroQOL-five dimensions (EQ-5D). WTP for a cure was elicited by double-bounded binary-choice questions followed by a bidding game. Psoriasis severity was graded as mild (PASI < 3), moderate, or severe (PASI ≥ 10). Results: The mean DLQI values for mild (n = 117), moderate (n = 208), and severe (n = 155) psoriasis were 5.73, 7.62, and 11.29, respectively. The mean health state utilities were 0.87 (EQ-5D), 0.72 (VAS), and 0.74 (TTO). The monthly maximum WTP value was US$145.3–318.8. EQ-5D and VAS scores were negatively correlated with all DLQI domains. WTP and DLQI also had a strong correlation in the expected direction. TTO had the weakest correlation with the DLQI. A smaller TTO was found for Taiwanese patients than for Caucasians. When considering different PASI severity levels, EQ-5D and VAS scores remained consistent measures for the DLQI, but the correlation between the TTO and DLQI weakened. Conclusion: The EQ-5D, VAS, and WTP are consistent measures for the DLQI in assessing the well-being of psoriasis patients in Taiwan