Zsa Zsa Weerts

Chapter 9 224 Table 9.2 Technical difficulties and consequences with regard to the digital symptom diary. Description of technical issue N patients affected Consequence and if applicable, solution. Low internet connectivity hindered installation of the application during the screening visit 15 In most cases, the problem was solved by moving to a location with better internet connectivity, or by postponing the installation to a later time. Not receiving push-notifications as a reminder to complete the end-of-day questionnaires 12 In many cases, patients would complete the questionnaire regardless of receiving the notification. However, the exact effect is unknown and it may have negatively impacted adherence during days no notification was received. In most cases, the problem could be resolved by changing the telephone settings, e.g. by ignoring battery optimizations. In two cases in which the issue could not be resolved, reminders were given during the study period by setting the alarm of the device at 10pm. In the short period during which it was unknown how many devices were affected, additional text-messages were sent as a reminder. Incomplete views of the questions due to a too large scaling on smaller smartphone screens. 8 The issue was resolved by adjusting the scaling in the application during updates. Because only a few letters were not depicted correctly and because all participants had received a manual that included the actual questions asked, the negative effect of short- term scaling issues is estimated to be negligible. iOS or Android updates that interfered with prior settings of the applications - The issue did not lead to missing data because the small bugs did not shut down the application. The development team would provide updates that resolved the issues as soon as possible. Maintenance of the hosting server 21 The issue led to missing data of one complete day, i.e. the day at which the maintenance took place, in all but 2 patients that were included at the time of the maintenance. Discussion The results of the current study demonstrate that patients’ adherence to the end-of-day questionnaire in the digital symptom diary was excellent, with a mean completion rate of 87.9% over 70 days of study duration. The total proportion of missing data and data-loss due to technical issues of the application was small, indicating that it is safe and realistic to use the application as a primary data-collection method. Furthermore, patients’ adherence to the web-based questionnaires and investigators’ adherence to the eCRF were also outstanding with completion rates of more than 99%.