Zsa Zsa Weerts

Chapter 9 222 -2 0 2 4 6 8 50 60 70 80 90 100 Weeks Adherence rate (%) Figure 9.4 Adherence rate per week to the digital symptom diary in the PERSUADE study, which was defined as the mean percentage of entries and calculated by dividing the number of actually completed entries over the number of minimal requested entries. Dots represent mean adherence rate (%) plus standard deviations. N =189. The decrease in adherence throughout the pre-treatment and treatment period is statistically significant, F(5.9, 1114.9)=15.5, P <0.001. When exploring independent baseline predictors for adherence, the combined regression model that included all minimization variables (age, gender, IBS-subtype, inclusion center), treatment group, baseline IBS symptom severity, anxiety and depression scores, and educational level, showed that one of the four inclusion centers, i.e. center C ( Supplementary Figure S9.2) , (regression coefficient B -10.04, 95% CI -19.51; -0.56, P =0.04) and anxiety scores at baseline (B -0.59, 95% CI -1.12; -0.06, P =0.03) were negatively associated with adherence throughout the study. Indeed, when comparing adherence between the different inclusion centers, mean (SD) adherence in center C was lowest, i.e. 82.3% (12.5), compared with 88.3% (9.2), 84.7 (14.0), and 91.4% (7.7), in centers A, B, and D, respectively. Mean time of completing the end-of- day symptom diary was 9:46 pm, i.e. 14 minutes before receiving the push notification. Feasibility of a smartphone application as primary data-collection method Several technical issues were noted by the investigators or reported by patients. In most cases, the cause was found and the issue was resolved by the app development team