What evidence is there for a relationship between organisational features and patient outcomes in congenital heart disease services? A rapid review
Authors: Turner Janette , Preston Louise , Booth Andrew , O’Keeffe Colin , Campbell Fiona , Jesurasa Amrita , Cooper Katy , Goyder Elizabeth 
Published: November 2014

Background

The purpose of this rapid evidence synthesis is to support the current NHS England service review on organisation of services for congenital heart disease (CHD). The evidence synthesis team was asked to examine the evidence on relationships between organisational features and patient outcomes in CHD services and, specifically, any relationship between (1) volume of cases and patient outcomes and (2) proximity of colocated services and patient outcomes. A systematic review published in 2009 had confirmed the existence of this relationship, but cautioned this was not sufficient to make recommendations on the size of units needed.

Objectives

To identify and synthesise the evidence on the relationship between organisational features and patient outcomes for adults and children with CHD.

Data sources

A systematic search of medical- and health-related databases [MEDLINE, EMBASE, Cumulative Index to Nursing and Allied Health Literature (CINAHL), The Cochrane Library and Web of Science] was undertaken for 2009–14 together with citation searching, reference list checking and stakeholder recommendations of evidence from 2003 to 2014.

Review methods

This was a rapid review and, therefore, the application of the inclusion and exclusion criteria to retrieved records was undertaken by one reviewer, with 10% checked by a second reviewer. Five reviewers extracted data from included studies using a bespoke data extraction form which was subsequently used for evidence synthesis. No formal quality assessment was undertaken, but the usefulness of the evidence was assessed together with limitations identified by study authors.

Results

Thirty-nine papers were included in the review. No UK-based studies were identified and 36 out of 39 (92%) studies included only outcomes for paediatric patients. Thirty-two (82%) studies investigated the relationship between volume and mortality and seven (18%) investigated other service factors or outcomes. Ninety per cent were from the USA, 92% were multicentre studies and all were retrospective observational studies. Twenty-five studies (64%) included all CHD conditions and 14 (36%) included single conditions or procedures. Although the evidence does demonstrate a relationship between volume and outcome in the majority of studies, this relationship is not consistent. The relationship was stronger for single-complex conditions or procedures. A mixed picture emerged revealing a range of factors as well as volume that influence outcome, including condition severity, individual centre and surgeon effects and clinical advances over time. We found limited (seven studies) evidence about the impact of proximity and colocation of services on outcomes, and about volume on non-mortality outcomes.

Limitations

This was a rapid review that followed standard methods to ensure transparency and reproducibility. The main limitations of the included studies were the retrospective nature, reliance on routine data sets, completeness, selection bias and lack of data on key clinical and service-related processes.

Conclusions

This review identified a substantial number of studies reporting a positive relationship between volume and outcome, but the complexity of the evidence requires careful interpretation. The heterogeneity of findings from observational studies suggests that, while a relationship between volume and outcome exists, this is unlikely to be a simple, independent and directly causal relationship. The effect of volume on outcome relative to the effect of other as yet undetermined health system factors remains a complex and unresolved research question.

Funding

The National Institute for Health Research Health Services and Delivery Research programme.