The magnitude and mechanisms of the weekend effect in hospital admissions: A protocol for a mixed methods review incorporating a systematic review and framework synthesis

A broad literature identifies that weekend admission to hospital, whether emergency [1, 2] or elective [3, 4], is associated with increased mortality. The impact on mortality is deferred—it occurs some days after weekend admission [5]. The cause for this effect is unclear, but is likely to be mediated partly through difference in case mix between weekdays and weekends and in part through different structures and processes of care at weekends, including the intensity of specialist provision and support services at weekends [6]. In the United Kingdom (UK), the National Health Service (NHS) has launched the 7-day services programme to create consistent quality of and access to health care throughout the week [7]. Quantifying the magnitude of the effect and understanding the underlying mechanisms by which improvements in patient outcomes might be achieved is important for justifying the investment required, and in differentiating effective interventions from secular trends.

The literature on the weekend effect is diffuse and rapidly growing [1, 2, 8‐11]. However, existing literature reviews have been limited by a focus on specific conditions and patient populations [8‐10], have not included quantitative synthesis [1, 2] or have lacked a detailed account of methodology [11]; none have systematically examined qualitative evidence. Given the ongoing controversies related to the subject and the need to have a better understanding of both the magnitude and mechanisms of the weekend effect to inform the planning, implementation and evaluation of any interventions and service re-design to tackle this issue, we will undertake a mixed methods review [12] of the literature as part of the High-intensity Specialist Led Acute Care (HiSLAC) Project, which brings together a broadly based coalition of patients, clinicians, researchers and policy-makers across the NHS in England to evaluate the impact of changes in specialist provision arising from NHS England’s 7-day services programme on the weekend effect. This protocol provides an overview of our methodological approach and detailed plan for the mixed methods review. The preparation of the protocol conforms to the PRISMA-P guidelines [13], and a completed PRISMA-P checklist can be found online [see Additional file 1].

The mixed methods review will include two complementary components: first, quantitative evidence will be synthesised to confirm the magnitude of the weekend effect and to identify possible moderators and mediators of the effect via a systematic review that incorporates meta-analyses. Second, we will use framework synthesis methodology [14, 15] to explore both qualitative and quantitative evidence on the mechanisms of the weekend effect.

This mixed methods review aims to quantify the magnitude of the weekend effect as well as provide greater insight into the mechanisms behind this complex phenomenon. Although a number of literature reviews have been conducted on related topics, they have either focused on specific disease conditions (e.g. myocardial infarction [8] and stroke [9]) or setting (e.g. intensive care units [10]) or adopted a ‘rapid review’ approach without detailed critical appraisal and quantitative synthesis of finding of individual studies [1, 2]. More importantly, an effort that systematically explore both the magnitude and possible mechanisms of the weekend effect through careful examination of diverse evidence, both quantitative and qualitative, appears to be lacking. Given the fast growing literature on this topic and the substantial public attention it has attracted, our proposed review is timely and will provide the best evidence to inform relevant debate and policy makers.

There are novel features in the mixed methods review that we propose here. First, given the complexity of the topic, we did not start with a rapid scoping search that is commonly adopted during the planning of a review. Instead, we undertook a comprehensive search using a broad and inclusive strategy to comprehensively capture potentially relevant studies, followed by an iterative and detailed screening process to gauge both the volume and nature of available evidence. This process, although time consuming, gives us a much better appreciation of the literature and allows us to prioritise our focus among the vast literature and to optimise the areas covered by the two components of the review. Second, the framework of the proposed review is informed not only by the expertise of the review team and the initial exploration of the literature, but also by focus groups that gathered the views of patients and health care providers. A similar, iterative process will be followed during the preparation of the review, providing further opportunities for wider participation and input from relevant stakeholders. This will help ensure the validity and relevance of the review methods and findings. Third, this review is undertaken alongside the five-year long HiSLAC project, which will generate further data on the magnitude and mechanisms of the weekend effect. The findings of the review can be updated when the new data become available and therefore will enable the new evidence to be incorporated into existing evidence and be interpreted in the context of the totality of available evidence. While this has long been advocated as the model for evidence based medicine and examples are growing for clinical trials [30], our adoption of this approach is relatively novel for observational health services research.

There are limitations to the planned systematic review. The volume of potentially relevant literature is large, and we have had to make a decision to focus on undifferentiated hospital admissions for the quantitative synthesis of weekend effect to ensure feasibility. Nevertheless, our detailed screening of records retrieved from our search will provide a comprehensive list of relevant studies on admissions related to specific conditions, which can be utilised for further systematic reviews in the future.

The topic of the weekend effect has attracted substantial attention among clinicians, academics and the general public. During our scoping and preparation of this protocol, we became aware of some concurrent work and expressed intention to undertaking review of literature in related fields [11, 31‐34]. While we believe our proposed review is the most comprehensive to date, a view confirmed by the advice of the HiSLAC project’s steering committee, we will be open to collaboration with other researchers to maximise knowledge gained through this effort and minimise potential duplication of work.