Relationship between volume and quality of health care: a review of the literature


The aim of this project was to carry out a systematic review of the literature in order to examine the evidence for a relationship between the volume of activity of a hospital and patient outcomes in a range of procedures.


Whilst most studies report a positive relationship between hospital volume and outcome for several elective procedures, they may have biased estimates of the size of the effect of volume because of poor adjustment for the effect of differences in case-mix between high and low volume hospitals. There is also a paucity of information as to why high volume might be associated with better outcomes. For example, there is little evidence whether clinician-related elements such as better judgement about high and low risk patients may be related to volume or whether high volume clinicians keep up with the literature and develop an effective protocol of practice. If the latter were true then the adoption of clinical guidelines by other clinicians may improve quality of care and close the gap between smaller and larger units. Alternatively, there may be institution related elements such as the level of facilities which produce better outcomes. There is also little evidence as to whether merging hospitals to create larger units will result in a change in outcomes over time. Because the uncertainty in both the size and the interpretation of any effect of volume reported, caution should be exercised in using this research literature to justify policies of reorganisation of health care delivery. Therefore, the main recommendation is that policy-makers should be cautious when invoking the assumed improvements in outcome achieved by volume as a key argument for centralisation of services.

Conducted by: Amanda Sowden1, Jon Deeks1, Ian Watt1, Trevor Sheldon1

1. NHS Centre for Reviews and Dissemination


NHS Centre for Reviews and Dissemination. Relationship between volume and quality of health care: a review of the literature. CRD Report 2. York: University of York. 1995

Sowden AJ, Deeks JJ, Sheldon TA. Volume and outcome in coronary artery bypass graft surgery: true relationship or artefact? BMJ. 1995;311(6998):151-5

Sowden A, Deeks J, Watt I, Sheldon T. Relationship between volume and quality in health care: a review of the literature. A report by the Yorkshire Collaborating Centre for Health Services Research (NHS Centre for Reviews and Dissemination). Leeds: Nuffield Institute for Health; 1995


Commissioned by the Department of Health