How have targets changed the way we organise emergency workloads and what has the impact been of the four-hour waiting target in accident and emergency? Paul Robinson explains

This analysis looks at emergency admissions to hospital, by discharging specialty (as this reflects where the patient was treated). In 2002, there were 64,000 admissions for A&E, of which 45 per cent were discharged on the day of admission - a zero length of stay (0LoS). By 2006 this was 331,000 (with 68 per cent having 0LoS).

In response to the introduction of the four-hour target at the end of 2004, many hospitals set up wards for short-term observation and to admit patients who would take longer than four hours to diagnose and treat. Some of these patients would previously have only been counted as A&E attenders - not emergency admissions. The target, it seems, has driven some of the increase in emergency admissions in England.

Across England emergency admissions have risen by 20 per cent in the past five calendar years (from 2002-06), an increase of three-quarters of a million patients a year. During this period, trusts have been working hard to improve the efficiency of admission processes.

Many have introduced medical admission units, and some surgical ones, so the most ill patients are seen as soon as possible by a consultant, who can diagnose, treat and discharge. This has led to a higher proportion of patients being discharged on the same day as admission, over a quarter (26 per cent) of all emergency admissions in 2006.

Of the total emergencies (723,000 patients), most of the growth has been in medicine, which treats around half of emergencies.

However, a surprisingly high proportion of the growth was in the A&E specialty: it accounted for 2 per cent of emergency admissions in 2002, but this had risen to 8 per cent in 2006.

Most of the growth in patients discharged on the day of admission has been in A&E.

There has been a lot of debate about the causes, which will be a combination of issues - among them changes in clinical practice, the GP contract and out-of-hours services, but particularly the introduction of the A&E four-hour target.