Table 1 Inclusion and exclusion criteria used for the screening process

 Study type

Publication date from 2000 present.

Studies from any geographical location.

English language.

Original qualitative studies, studies involving secondary analysis of qualitative data or qualitative studies that are part of a mixed methods study (e.g. the study also has a quantitative component but the major component is qualitative and a qualitative methodology is described). The study must have direct contact with individuals or direct observation using any form of qualitative method.

 Participant Type

Any individual (adult or child). This includes patients, the public and health professionals who would be aware of the experiences of these groups.

 Type of digital health intervention

Any health intervention delivered by a digital technology (hypothetical or in development, simulated or real-world) which takes information from patients or the public or provides some form of advice or feedback about their health. This includes, but is not limited to:

• Web-based interventions on personal computers (PCs) or mobile platforms,

• Mobile health applications or apps,

• Patient portals or personal health records,

• Interventions delivered by short message service (SMS) or interactive voice recognition (IVR).

 Setting

Any ‘usual’ setting (hypothetical or in development, simulated or real-world) such as primary, secondary or tertiary care, the home or workplace.

 Phase of implementation

Engagement and recruitment phase of a digital health intervention, which can span from gauging an individual’s readiness for a digital health intervention, to the initial marketing or reach of the initiative, to actively signing individuals up to use the technology so they are registered on the digital application or system.

 Study Type

Published pre 2000.

Non English language.

Grey literature/not published in a peer reviewed journal.

Dissertation/thesis.

Published abstracts or conference proceedings.

Studies using the following methodologies: descriptive case studies, lexical studies that analyse natural language data presented as qualitative results; qualitative studies using questionnaires or other methods that do not involve direct contact or observation of participants.

Any type of literature review, systematic review and meta-analyses, or a qualitative study that did not involve direct contact or observation of participants.

Randomized Controlled Trials due to the large volume of literature on the difficulties recruiting to clinical trials that already exists [94].

Commentary articles, written to convey opinion or stimulate research/discussion, with no research component.

 Type of digital health intervention

Primary digital intervention is; telephone based with no additional technological function (e.g. telephone counselling or triaging service); Internet based with no additional interactive function (e.g. searching for health information online); or an implantable device that is remotely monitored

 Setting

Any non-usual setting e.g. prison, armed forces in active duty.

 Stage of implementation

Pre-implementation work based solely around designing the interface and functionality of the digital health intervention.

The post engagement/recruitment phase will not be explored. For example:

• why patients or the public use or do not use digital health interventions,

• why they drop out (attrition) or fail to continue using them (retention),

• their attitudes or beliefs towards digital health interventions, or their satisfaction with them outside of that pertaining directly to engagement and recruitment.