“…In two studies [61,62], choices given to participants' comprised the following WTP categories: US$1000, US$5000, US$10,000, US$25,000, and US$50,000. In Smit et al [63], the options to be considered were listed as a proportion of the participant's monthly income and ranged from less than one fourth to more than 20 times. Various generic preference-based HRQoL instruments were used to calculate QALYs: HUI2 (n = 1) [58], HUI3 (n = 2) [53,58], EQ-5D (n = 3) [53,57,58], SF-6D [58] (n = 1), and QWS (n = 2) [55,56].…”