Background: Patient-reported outcomes are vital in informing randomised controlled trials (RCTs) and health-care interventions and policies from the patient's perspective. However, participant non-response may introduce bias and can affect the generalisability of the trial. This study evaluates two interventions aimed at increasing response rates to postal questionnaires within a large, UK-wide RCT: pre-notification via short messenger service (SMS) text prior to sending the initial mailing of trial questionnaires versus no pre-notification; for non-responders to the initial mailing of the questionnaires, an e-mail reminder (containing a hyperlink to complete the questionnaire online) versus a postal reminder.
Methods: This study is a 2x2 partial factorial design RCT nested within an RCT of medical expulsive therapy for ureteric stone disease. Participants who supplied a mobile telephone number were randomly assigned to receive an SMS text pre-notification of questionnaire delivery or no pre-notification. Those who supplied an e-mail address were randomly assigned to receive a questionnaire reminder by e-mail or post. Participants could be randomly assigned to the pre-notification comparison or the reminder comparison or both. The primary outcome measure was response rate at each questionnaire time point.
Results: Four hundred eighteen participants were randomly assigned to the SMS pre-notification comparison (80 % were male, and the mean age was 41 years with a standard deviation (SD) of 11.1). The intervention had no effect on response rate at either questionnaire time point. In subgroup analyses, SMS pre-notification increased response rates in women but only at the first questionnaire time point. One hundred nineteen participants were randomly assigned to the reminder comparison (80 % were male, and the mean age was 42 years with an SD of 12.1). There was no difference in response rate in those who received an e-mail reminder compared with those who received a postal reminder.
Conclusions: SMS text pre-notification of questionnaire delivery and email delivery of questionnaire reminders did not improve response rates. There was some evidence to suggest that SMS text pre-notification may be effective in women, and further studies to investigate this may be warranted. E-mail reminders for participants to return their postal questionnaire could be advantageous given that response rates were similar following either type of reminder and the low cost of delivering an e-mail compared with a postal reminder.
SUSPEND was funded by the National Institute for Health Research (NIHR) Health Technology Assessment (HTA) Programme (project 80/71/01) and will be published in full in Health Technology Assessment. The Health Services Research Unit of the University of Aberdeen is funded in part by the Chief Scientist Office of the Scottish Government Health and Social Care Directorates. The views and opinions expressed herein are those of the authors and do not necessarily reflect those of the Chief Scientist Office, HTA programme, NIHR, National Health Service, or Department of Health. The authors thank the SUSPEND staff and participants, without whom this study would not have been possible.
- Randomised controlled trial
- Short messenger service (SMS)
- Electronic mail (e-mail)