Analysis methods
The psychometric evaluation of NASH-CHECK was conducted in two stages: first, item-level evaluations to inform item reduction and determine the optimal scale structure; and second, scale-level evaluations to assess the properties of the identified scales. For item-level analyses, the Part B and C data were analyzed separately. Most scale-level evaluations were conducted using the pooled Part B and C data, except for test–retest reliability (for which appropriate test–retest assessments were available only in Part C) and responsiveness (for which change from baseline to week 48 using Part C data was evaluated in addition to change from baseline to week 12 using the pooled Part B and C data). A summary of the data used for each analysis is presented in Additional file Missing visit-level data were not imputed for any of the study measures. NASH-CHECK data were analyzed as observed, with no imputation of missing items. All other PRO measures were scored according to the respective instrument’s scoring guidelines.