The findings support policies to reduce the time patients wait and call into question government plans to abandon the 4-hour A&E target in England for lack of "clinical justification."

Long emergency department waiting times are associated with delays in care and several countries have set targets for the time patients wait. Most (85%) of emergency department patients go home after their visit, but whether waiting times adversely affect their outcomes is unknown.

So researchers in Canada set out to determine whether patients who present to emergency departments during shifts with long waiting times are at risk for adverse events (hospitalisation or death within seven days).

Using data from high volume emergency departments in Ontario, Canada from 2003-2007, they identified 13,934,542 "seen and discharged" patients and 617,011 "left without being seen" patients.

Risk of short term adverse events increased with average emergency department length of stay.

Although the overall risk is low, risk of hospital admission increased by up to 95% while risk of death increased by up to 79% among the sickest patients.

Risk of death increased incrementally with each additional hour of average shift waiting time and the authors calculate that reducing emergency department length of stay by one hour, on average, could have potentially cut the number of deaths in this study in higher risk patients by 558 (6.5%) and in lower risk patients by 261 (12.7%).

Contrary to popular belief, patients who left without being seen were not at higher risk of short term adverse events compared with patients who were seen and discharged, nor were patients who attended emergency departments with high "left without being seen" rates.

This is reassuring, say the authors, as there has been much uncertainty surrounding outcomes of "left without being seen" patients. However, these results suggest that presenting to emergency departments during shifts with long average waiting times may have serious patient safety implications.

They argue that there is likely clinical justification to reduce emergency department waiting times and they call into question recently announced plans to abandon English emergency department targets.

In an accompanying editorial, Melissa McCarthy, Associate Professor at George Washington University in the US writes: "We need to extend the evaluation of emergency care to either the resolution of the problem or transfer of care to a provider better suited to tackle the patient's needs."

She believes that emergency departments must be redesigned to meet patients' needs more effectively and efficiently. Ongoing measurement of patient outcomes is also essential, she says, as is seamless integration between the emergency department and hospital and a stronger linkage to ambulatory care providers to enhance delivery of care and clinical effectiveness.

Note: If no author is given, the source is cited instead.

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