Intended for healthcare professionals


Analysis of the distribution of time that patients spend in emergency departments

BMJ 2005; 330 doi: (Published 19 May 2005) Cite this as: BMJ 2005;330:1188
  1. Thomas E Locker ({at}, research fellow in emergency medicine1,
  2. Suzanne M Mason, clinical senior lecturer in emergency medicine1
  1. 1Medical Care Research Unit, School of Health and Related Research, University of Sheffield, Sheffield S1 4DA
  1. Correspondence to: T Locker
  • Accepted 22 March 2005


The NHS Plan stated: “By 2004 no one should be waiting more than four hours in Accident and Emergency from arrival to admission, transfer or discharge.”1 This target was changed to allow for certain clinical exceptions, and since January 2005, 98% of patients must spend less than four hours there.2 We analysed the distribution of time spent by patients in emergency departments in England.

Participants, methods, and results

We invited major emergency departments (those providing 24 hour cover and most core services) in England to submit data for each new patient attending during April 2004. We determined the distribution of total time in each department for patients who were admitted to hospital and for those discharged from the department. To assess the generalisability of these findings, we used performance data from the Department of Health to compare trusts in which at least one department had submitted data or in which no department had.3

We received data from 83 departments detailing 428 593 clinical episodes. Of these episodes, 72.8% (n = 311 957) resulted in discharge and 22.0% (n = 94 200) in admission. Of the remaining episodes, 1% (n = 4452) were transferred, 0.2% (n = 975) died, and 3.9% (n = 16 504) did not wait to be seen. In 0.1% (n = 505) of episodes the outcome was unknown. The figure shows the distribution of total time in the emergency department for episodes resulting in admission or discharge.


Distribution of total time in emergency department for episodes resulting in admission or discharge

The median total time in the department for discharged patients was 96 minutes (98th centile = 341 minutes); 91.0% (n = 283 894) of these patients spent < 220 minutes in the department, with a further 3.6% (n = 11 161) spending 220-239 minutes. We calculated separately for each department the mean age of patients spending 220-239 minutes there and of those spending < 220 minutes there. A comparison using a paired t test showed that the mean age of the latter group (32.9 years) is significantly lower than that of the group who spent more time in the department (42.8 years) (t(df = 82) = 19.8, P < 0.001).

Patients admitted from the emergency department had a median total time in the department of 183 minutes (98th centile = 625 minutes). The distribution of total time in the department for patients admitted from the emergency department shows the most striking anomaly, with 64.0% (n = 60 315) of patients spending < 220 minutes in the department and a further 12.3% (n = 11 563) spending 220-239 minutes. Admitted patients spending 220-239 minutes in the department were also significantly older than those spending < 220 minutes there (mean age 56.5 v 48.9 years; t(df = 82) = 8.28, P < 0.001).

In 60 trusts at least one emergency department had submitted data for the study, and in 92 none had. The mean percentage of patients spending less than four hours in the emergency department in these two groups was 93.16% and 93.68% respectively. This difference was not significant (t(df = 150) = 1.08, P = 0.28).


Although the departments studied performed well, older patients and those who were subsequently admitted were in the emergency department for longer than others, reflecting the findings of the recent National Audit Office report.4 Our interpretation of these findings is limited by the lack of national data on the distribution of total time in emergency departments before the introduction of the four hour target. Response times for ambulance services in England have a similar distribution that peaks just before the target time.5 Such performance targets should be monitored in such a way that any improvement can be shown to represent meaningful improvement in the patient's experience of the healthcare system.

What is already known on this topic

Data published by the Department of Health show that the performance of emergency departments in England has improved when assessed by the proportion of patients treated within the current government target of four hours

What this study adds

One in eight patients who are subsequently admitted are moved out of the emergency department in the final 20 minutes of the four hour target period

This article was posted on on 20 April 2005:


  • Contributors Both authors designed the study, interpreted the data, and revised the final text. TEL is the guarantor for the paper.

  • Funding This study was conducted as part of a study funded by the National Co-ordinating Centre for NHS Service Delivery and Organisation Research and Development. The funding body was not involved in the design or analysis or in the decision to publish this study.

  • Competing interests None declared.

  • Ethical approval The study was approved by Eastern Medical Research Ethics Committee.


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