Updated normative data for the EORTC QLQ-C30 in the general Dutch population by age and sex: a cross-sectional panel research study.

"Declarations Conflict of interestSN: received grant EORTC Quality of Life Group grant #001 2015 (payments were made to Charité – Universitätsmedizin Berlin, Germany); was employed as a consultant/director by ICON plc from September 2018 to June 2021 and by Union Chimique Belge Biosciences GmbH from July 2021 until December 2021. The other authors declare that they have no competing interests. Ethics approval and consent to participateNo ethics approval was sought as the study is based on panel data. According to the NHS Health Research Authority and the European Pharmaceutical Market Research Association (EphMRA), panel research does not require ethical approval if ethical guidelines are followed. The survey was distributed via the GfK SE (member of EphMRA) and obtained informed consent by each participant before the study. All data were collected anonymously and identification of the respondents through the authors is impossible. Conflict of interest SN: received grant EORTC Quality of Life Group grant #001 2015 (payments were made to Charité – Universitätsmedizin Berlin, Germany); was employed as a consultant/director by ICON plc from September 2018 to June 2021 and by Union Chimique Belge Biosciences GmbH from July 2021 until December 2021. The other authors declare that they have no competing interests."

"Funding Open Access funding enabled and organized by Projekt DEAL. This research was partly funded by the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Group (Grant No. 001 2015)."