[Emergency department overcrowding: quantification of associated factors]

Emergency department (ED) overcrowding has been increasing over the last years. The aims are to define ED overcrowding, and to determine and quantify which factors explain it.

For 3 consecutive weeks throughout 3 years (2000-2002), we recorded every 3-hour period, the arrivals, the occupancy rate (OR) of patients in ED, in first aid area (FAA), and in observation area (OA) according to the reason for their stay. The data was subjected to multiple logistic regression analysis including as a dependent variable non overcrowding/overcrowding for each area (ED, FAA, and OA). Overcrowding was defined as an OR >= 100%. Models from the three areas were calculated according to goodness of fit and were discriminated by ROC methodology. Models were set up after randomizing data in two groups: selection set (88% of data) and validation set (12% of data).

Variables associated with overcrowding in the ED model were OR of patients waiting for test results, for a bed going to be left, to find a bed, for test performed out of ED, and for outcome. In the FAA model, they were OR of patients being seen, and waiting for test results. Finally, in the OA model they were OR of patients waiting for a bed going to be left, to find a bed, for test performed out of ED, and for outcome. For all models sensitivity and specificity were greater than 85%, with a ROC area greater than 0.97. We did not find any relationship between number of arrivals and overcrowding for none model. Results were corroborated on the validation data set.

Patients remaining in the ED due to factors related to both hospital (waiting for a bed going to be left, or to find a bed), and ED itself (waiting for outcome) are the main reason for ED overcrowding.