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Chapter 8 208 Supplementary Results Compliance and missing data Compliance to the web-based questionnaires was high : only a single patient did not complete the questionnaires at the end of the treatment period. All other patients completed all questionnaires until the end of the study or until discontinuation. However, due to a routing error, a single question regarding presenteeism was not presented to all patients at all time points. This led to missingness of this particular item in up to 50% of patients. Missingness on this topic was well balanced between treatment groups and the missing values were MCAR. Missing values regarding costs and utilities from the patients that discontinued the study ( N =6) were MAR. No other missing values occurred. An overview of the proportion of patients with missing data per cost component is given in Supplementary Table S8.1 .