The four primary care (PC) core functions (the ‘4Cs’, ie, first contact, comprehensiveness, coordination and continuity) are essential for good quality primary healthcare and their achievement leads to lower costs, less inequality and better population health. However, their broad definitions have led to variations in their assessment, in the innovations implemented to improve these functions and ultimately in their performance.

To update and operationalise the 4Cs’ definitions by using a literature review and analysis of enhancement strategies, and to identify innovations that may lead to their enhancement.

Narrative, descriptive analysis of the 4Cs definitions, coming from PC international reports and organisations, to identify measurable features for each of these functions. Additionally, we performed an electronic search and analysis of enhancement strategies to improve these four Cs, to explore how the 4Cs inter-relate.

Specific operational elements for first contact include modality of contact, and conditions for which PC should be approached; for comprehensiveness, scope of services and spectrum of population needs; for coordination, links between PC and higher levels of care and social/community-based services, and workforce managing transitions and for continuity, type, level and context of continuity. Several innovations like enrolment, digital health technologies and new or enhanced PC provider’s roles, simultaneously influenced two or more of the 4Cs.

Providing clear, well-defined operational elements for these 4Cs to measure their achievement and improve the way they function, and identifying the complex network of interactions among them, should contribute to the field in a way that supports efforts at practice innovation to optimise the processes and outcomes in PC.

To provide an overview of the current state of research of advance care planning (ACP), highlighting most studied topics, publication time, quality of studies and reported outcomes, and to identify gaps to improve ACP receptivity, utilization, implementation, and outcomes.

Cochrane methodology for conducting overviews of systematic reviews. Study quality was assessed using a modified version of the Assessing the Methodological Quality of Systematic Reviews tool. The following databases were searched from inception to April 2017: MEDLINE, EBM Reviews, Cochrane Reviews, CINAHL, Global Health, PsycINFO, and EMBASE. Searches were supplemented with gray literature and manual searches.

Eighty systematic reviews, covering 1,662 single articles, show that ACP-related research focuses on nine main topics: (1) ACP as part of end-of-life or palliative care interventions, (2) care decision-making; (3) communication strategies; (4) factors influencing ACP implementation; (5) ACP for specific patient groups, (6) ACP effectiveness; (7) ACP experiences; (8) ACP cost; and (9) ACP outcome measures. The majority of this research was published since 2014, its quality ranges from moderate to low, and reports on documentation, concordance, preferences, and resource utilization outcomes.

Despite the surge of ACP research, there are major knowledge gaps about ACP initiation, timeliness, optimal content, and impact because of the low quality and fragmentation of the available evidence. Research has mostly focused on discrete aspects within ACP instead of using a holistic evaluative approach that takes into account its intricate working mechanisms, the effects of systems and contexts, and the impacts on multilevel stakeholders. Higher quality studies and innovative interventions are needed to develop effective ACP programs and address research gaps.