This study aimed to validate the EQ-5D-5L with the addition of skin irritation and self-confidence bolt-on items in Chinese patients with urticaria.
The skin irritation and self-confidence bolt-on items were translated into Simplified Chinese and cognitively debriefed. A cross-sectional survey was subsequently conducted among patients diagnosed with urticaria in Guangdong Province, China. The questionnaire included the EQ-5D-5L with the 2 bolt-on items, along with the Dermatology Life Quality Index (DLQI) and Skindex-16. The study examined the ceiling effects, informativity, and known-group validity of the 2 bolt-on items. Multiple regression analysis was conducted to determine the explanatory power of the EQ-5D-5L and bolt-on items in predicting the EQ VAS.
A total of 475 patients completed the questionnaire and were included in the analysis. The inclusion of the 2 bolt-on items reduced the ceiling effect from 54.95% to 4.21%. The skin irritation item showed a greater correlation with DLQI item 1 and the symptoms dimension of the Skindex-16 (correlation coefficients: 0.39 and 0.31, respectively). The self-confidence item exhibited a moderate correlation with DLQI item 2 (r = 0.42) and the functioning dimension of the Skindex-16 (r = 0.33). Known-group validity analysis confirmed that the skin irritation item demonstrated satisfactory discriminatory power. Multiple regression analyses indicated that the inclusion of skin irritation enhanced the explanatory power for EQ VAS more effectively than self-confidence.
The inclusion of 2 bolt-ons in the EQ-5D-5L enhanced its informativity, convergent validity, discriminatory power, known group validity, and explanatory power among Chinese patients with urticaria.