Emergency Department utilisation: a natural experiment

In February 2005 a new Emergency Department (ED) was opened at Waitakere Hospital in West Auckland, New Zealand. Part of the rationale for this was the expectation that it would reduce attendances to the four established EDs in the Auckland region. This study was undertaken to determine whether this happened.

A retrospective analysis of ED presentations to Auckland City, Starship and North Shore hospitals for the 2 years prior to the opening of Waitakere ED (February 2005) was conducted. This was compared with the attendances to all hospitals in the 2 years following the opening of the new ED. The effect of the opening of Waitakere ED on ED presentations to other hospitals was assessed using control charts. Presentations to Middlemore Hospital during the same time period were used as a control.

ED attendance to hospitals in the Auckland District Health Board (DHB) area increased by 9% over the study period (Auckland Hospital = 13%, Starship Children's Hospital = 2%), similarly ED attendance to Middlemore Hospital increased by 6%, consistent with population growth. However ED attendance to hospitals in the Waitemata DHB area (North Shore and Waitakere Hospitals) increased by 74%, disproportionate to population growth (8%).

The opening of a new ED may have contributed to an increase in total ED presentations seen within the region overall, with no corresponding reduction in attendances at neighbouring hospitals.