To conduct a synthesis of existing empirical and grey literature to identify the contexts and mechanisms that enable the adoption, offer, uptake and return of faecal immunochemical testing (FIT) in the primary care pathway in England, UK, for patients with signs or symptoms of suspected colorectal cancer (CRC). From this, develop a theory about how specific programme activities lead to certain outcomes.

A realist synthesis.

Medline (OVID), EMBASE (OVID), CINAHL (EBSCO), Scopus (Elsevier) and grey literature sources until end of July 2023.

The purpose of the work was to determine how different factors interact within a health system to optimise the approach to implementing and using symptomatic FIT (sFIT) in clinical practice for patient benefit. The criteria used to bound the scope of the synthesis included date (published between 2017 and July 2023), exposure of interest (sFIT in the primary care pathway for patients with signs or symptoms of suspected CRC), geographic location of study (countries that make up the UK), language (English) and participants (adults). Any study design and type of publication was considered.

Given the recognised lack of literature on the implementation of sFIT, it was crucial to include insights from grey literature. To do this, key national groups and organisations—involved or related to this subject—were methodically identified and appropriate papers and reports identified.

A thematic approach was used to identify relevant data in included records and allow realist insights to be obtained. Inductive and deductive coding enabled detection of key data. Arguments were generated and developed into context–mechanism–outcome configurations (CMOCs). Iteratively, an initial list of 38 CMOCs was refined to 14 themes and 19 CMOCs. These were then structured to create a multifaceted, multilevel realist synthesis programme theory.

Systematic searching led to the full appraisal of 99 records to determine suitability of each to confirm, refute or help develop theory. Studies were assessed for rigour and relevance to inform selection. The process resulted in 45 records being chosen for inclusion, of which 28 were from database searches and 17 from grey literature sources.

The key contexts and mechanisms that help optimise adoption, offer, uptake and return of sFIT have been elucidated (although partially). These can be broadly summarised into the 10 ‘Cs’: creating a compelling Case and Conditions for change, reaching Consensus through Collaborative working, fostering a Culture that values Clinical judgement, building Confidence by developing Capabilities and, finally, ensuring Clarity and Coherence of both practical processes and safety netting procedures.

Fundamentally, optimising the adoption, offer, uptake and return of sFIT in primary care for patients with signs or symptoms of suspected CRC is predicated on developing the acceptability of this initiative to every stakeholder at every level within a health system.