For many years, clinicians, managers and policy-makers have tried various strategies to reduce hospital admissions, but rates have continued to increase.

A particular focus has been on patients with conditions where timely access to high quality primary and preventative care can avoid the need for hospital admission in most cases.

These conditions are known as ambulatory-care sensitive (ACS). Aggregate rates of emergency admissions for ACS conditions are commonly used to measure how well the health system is preventing unplanned hospital use.

We were interested to understand how these rates varied across areas, and how they have changed over time – particularly in relation to the recent financial constraints introduced in the NHS.

To do this we used an anonymised record of all hospital admissions in England between April 2001 and March 2013; nearly 200 million episodes of care. We used the most common definition for ACS conditions and standardised rates for age, sex and in some cases deprivation of the population.

20% of emergency admissions were for ACS conditions

Analysis of the data shows that 20% of emergency admissions were for ACS conditions and the rate of admission (standardising for age and sex) has grown by 26% since 2001/02.

There was also substantial variation in rates of admission between areas. A substantial amount of the variation is related to deprivation, which must be considered when using ACS conditions as markers of health outcomes.

The variation that does not appear to be related to deprivation implies that reductions in ACS admissions can be achieved in areas with higher rates; but only if approaches developed in areas with lower rates can be transferred effectively.

Trends in admission do not appeared to have changed significantly since the introduction of current financial constraints.