Developing Digital Interventions: A Methodological Guide

Table 1

Key steps and common critical issues in developing DIs.

Key steps	Common critical issues
Intervention planning
What are the key behaviours to be targeted?
What modality is most appropriate for delivery (e.g., computers, smartphones, or text messages)?
Determine likely influences on key behaviours using; (i) deductive reviews of the literature and implementation of theory,; (ii) inductive research with users and stakeholders.	Ensure both quantitative and qualitative literatures are reviewed to fully understand likely effectiveness and acceptability of DI components.
Create an intervention plan.; (i) What should the intervention contain to maximise effectiveness, acceptability, and feasibility?; (ii) When should each intervention component be introduced to the user?; (iii) Plan practical aspects of the DI (such as security and logging on procedures).	Include a security page to allay user concerns.; Make the logging on button larger than the register button to avoid problems with users registering multiple times.
Prioritise intervention components to ensure feasibility for the development team.
Intervention development and usability testing
(i) Think-aloud interviews to assess user perceptions and interactions with the intervention.; (ii) Modify the DI as needed.	Be sure to observe how users navigate the intervention during think-aloud interviews as this provides additional information about potential problems.
Retrospective interviews with users who have tried the intervention alone.	Try to conduct interviews within a week of the participant using the DI to maximise recall.; Users can keep a diary of their experiences of using the DI to improve recall during interviews.
(i) Triangulate user data (e.g., aspects of DI viewed) with retrospective interview data to gain a fuller picture of how the DI is used when participants are alone.; (ii) Modify the DI as needed.
Intervention testing
Feasibility RCT to test the study processes for a full trial.	Retrospective interviews can highlight ways to improve study processes or the DI for the main trial.
Fully powered RCT to test the effectiveness and cost-effectiveness of the DI.	Retrospective interviews can enhance interpretation of quantitative results.