Zsa Zsa Weerts

Chapter 9 214 the adherence to the assessment method used, and data on adherence in other populations can not necessarily be extrapolated to IBS. Therefore, our primary aim was to evaluate the performance of a custom-made digital symptom diary in patients with IBS, in particular by assessing patients’ adherence. Since patient characteristics can impact adherence 17,18 , our secondary aim was to identify sociodemographic and clinical patient characteristics associated with adherence rate. Materials and methods The present study was based on data from the PERSUADE study. 16 This was a randomized, double-blind, placebo-controlled trial conducted in four hospitals located throughout the Netherlands ( Supplementary Figure S9.1) . The study protocol was approved by the Maastricht University Medical Center+ (MUMC+) Ethics Committee and was registered in the US National Library of Medicine (Clinicaltrials.gov; NCT02716285). All study procedures were performed in compliance with Good Clinical Practice Guidelines and according to the revised Declaration of Helsinki. 19 All participants gave written informed consent prior to participation. The study design of the PERSUADE study has been described in detail elsewhere. 16 In brief, the primary aim was to investigate the efficacy of peppermint oil, a conventional small-intestinal and a novel ileocolonic release formulation, in patients with IBS. To this end, patients between 18-75 years of age, who fulfilled the Rome IV-criteria for IBS and had a mean worst abdominal pain score at least 3 on an 11-point numerical rating scale (NRS, 0=no pain, 10=worst possible pain) during a 14-days pre-treatment period were included. Participants were randomized to placebo, small-intestinal release peppermint oil, or ileocolonic release peppermint oil for an eight-week treatment period. Data-collection was performed using a customized framework for digital data-collection, specifically designed and developed for the trial, consisting of 1) a digital symptom diary (smartphone application); 2) an electronic Case Report File (eCRF, Castor EDC); 3) web-based patient questionnaires (Castor EDC); and 4) a planning tool (Ldot). During the 14-days pre-treatment and the eight-week treatment period, patients were instructed to register symptoms daily in the digital symptom diary. Study visits and telephone follow-up telephone interviews were documented in the eCRF. Patients were requested to complete several web-based questionnaires at different time-points within the study duration. The complete list of inclusion criteria and study overview with timing