Volume and outcome in hospital care: evidence, explanations and implications.

The relationship between the volume of work undertaken in a hospital and the outcome of care has assumed increasing importance in recent years. A review of the literature reveals that most studies have been carried out in the USA and have largely been confined to six specific areas of health care. There is evidence that better outcomes are obtained at higher volumes for several surgical operations, cardiac catheterisation and care of the severely injured. As yet there is no clear association for coronary, neo-natal and burn care. There are two competing hypotheses to explain any association -- 'practice-makes-perfect' and 'selective referral'. These are discussed and implications for the future provision of hospital services considered.