To determine if a new outpatient preauthorization process for radiologic studies was associated with a change in emergency department (ED) CT and MRI utilization rates. Methods: This was a retrospective study set in an urban tertiary teaching hospital. Subjects included all nonadmitted ED patients who had either a CT or MRI during a control or preauthorization period. The study group consisted of those patients whose insurance required preauthorization. The control group consisted of those patients for whom preauthorization was not required. We used a multiple regression with autoregressive error adjusting for seasonal and monthly variation to obtain the rates of change of CT and MRI usage over time for the control and preauthorization periods.

The control period consisted of 29,303 ED visits over 54 weeks not resulting in hospital admission. The preauthorization period contained 33,858 patients over 64 weeks. The baseline ordering of CT and MRI was not significantly different between the groups. After controlling for seasonal and monthly variation, our results demonstrated that while both insurance groups demonstrated an increase in use of CT and MRI from the control to preauthorization periods, there is a statistically significant increase only in the rate of MRI utilization in the study group during the preauthorization period.

A telephone preauthorization process for radiological studies produced a statistically significant change in the rate of ordering MRI studies, but not CT, in the study group. We conclude that this preauthorization process may have resulted in additional ED visits for outpatient MR scans.