Discussion
vitiligo
VITILIGO
We have provided a way of estimating EQ-5D utilities from two vitiligo specific HRQoL instruments and shown a relationship between CSMs of HRQoL and clinical outcomes such that plausible clinical cut-off scores for RPS can be associated with HRQoL. Several useful mapping algorithms with adequate performance characteristics when compared to available mapping algorithms [There are several limitations to this research. Firstly, all published mapping algorithms when applied to independent data will reflect differences in factors such as patient characteristics, trial conditions and assessment points. Secondly, by 9 months only around 60% of the data in the HI-Light trial were available for the mapping model and the data did not include a complete range of EQ-5D-5 L health states; thirdly, scales such as the VNS and RPS are discrete and as such patient level modelling tends to classify predictions into a limited number of possibilities. Fourthly, in an attempt to anchor clinical outcomes with HRQoL, the chance of no or little noticeability did not exceed much more than 20%, despite high HRQoL benefits in measures such as EQ-5D and Total VitiQoL score. Finally, there is a concern that a mapped utility has no known immediate health state (a type of double mapping): for example, a utility value of 0.193 has a health state of '11153', whereas a predicted (mapped) utility of 0.866 has no known health state profile (UK tariff). However, this is also true for any mean utility computed from known health states and therefore would not seem to be a valid objection. Despite these limitations, the mapping algorithms presented are a ‘first’ in vitiligo that compares two different crosswalks with performance metrics similar or better to that reported in mapping literature. In addition, we provide a basis for further research in delineating cut-off scores that can anchor clinical outcomes such as RPS with HRQoL.