UCSF

Objective

There has been a rise in advanced diagnostic imaging (ADI) use in the emergency department (ED). Increased utilization may contribute to longer length of stay (LOS), but prior reports have not considered improved methods for modeling skewed LOS data.

Methods

The 2010 National Hospital Ambulatory Medical Care Survey data were analyzed by 5 common ED chief complaints. Generalized linear model (GLM) was compared to quantile and ordinary least squares (OLS) regression to evaluate the association between ADI and ED LOS. Receipt of computed tomography or magnetic resonance imaging was the primary exposure. Emergency department LOS was the primary outcome.

Results

Of the 33,685 ED visits analyzed, 17% involved ADI. The median LOS for patients without ADI was 138 minutes compared to 252 minutes for those who received ADI. Overall, GLM offered the most unbiased estimates, although it provided similar adjusted point estimates to OLS for the marginal change in LOS associated with ADI. The effect of imaging differed by LOS quantile, especially for patients with abdominal pain, fever, and back symptoms.

Conclusions

Generalized linear model offered an improved modeling approach compared to OLS and quantile regression. Consideration of such techniques may facilitate a more complete view of the effect of ADI on ED LOS.