Background
The use of mobile messaging including Short Message Service (SMS) and Web-based messaging in healthcare has grown significantly. Using messaging to facilitate patient communication has been advocated in several circumstances including population screening. These programmes, however, pose unique challenges to mobile communication, as messaging is often sent from a central hub to a diverse population with differing needs. Despite this, there is a paucity of robust frameworks to guide implementation.

Objective
This protocol describes the methods that will be used to develop a guide for the principles of use of mobile messaging for population screening programmes in England.

Methods
This modified Delphi study will be conducted in two parts: evidence synthesis and consensus generation. The former will incorporate a literature review of publications from 1st January 2000 to the present. This will elicit key themes to inform an online scoping questionnaire posed to a group of experts from academia, clinical medicine, industry and public health. Thematic analysis of free-text responses by two independent authors will elicit items to be used in the consensus generation. Patient and Public Involvement groups will be convened to ensure that a comprehensive item list is generated, which represents the public’s perspective. Each item will then be anonymously voted upon by experts as to its importance and feasibility of implementation in screening, during three rounds of a Delphi process. Consensus will be defined a priori at 70%, with items considered important and feasible eligible for inclusion into the final recommendation. A list of desirable items (important, but not currently feasible) will be developed to guide future work.

Results
The Institutional Review Board at Imperial College London has granted ethical approval (20IC6088). Results are expected to involve a list of recommendations to screening services with findings made available to screening services through Public Health England. This study will thus provide a formal guideline for the use of mobile messaging in screening services and provide future directions in this field.

Discussion
The use of mobile messaging has grown significantly across healthcare services, especially given the COVID-19 pandemic, but its implementation in screening programmes remains challenging. this modified Delphi approach with leading experts, will provide invaluable insights to facilitate incorporating messaging in these programmes, and create awareness of future developments in this area.