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Trends in case-mix-adjusted use of radiology resources at an urban level 1 trauma center.

OBJECTIVE
The objective of our study was to determine the utilization rates of diagnostic radiology services at an urban level 1 trauma center.


MATERIALS AND METHODS
This was an observational study of imaging use patterns from 1993 to 1998. Data were segregated by patient type and imaging procedure. Annual hospital admissions were adjusted for severity of illness using the Health Care Financing Administration's case-mix index. Per-patient imaging trends for the emergency department and outpatients were assessed using a ratio of the total number of procedures to the number of patient visits. Linear regression models were used to assess the strength of associations between resource use, measured as relative value units (RVUs), and independent variables (calendar year, patient type, and examination type).


RESULTS
The RVUs for all imaging increased 53% for inpatients, 69% for outpatients, and 85% in the emergency department. No significant trend for use was found for the aggregate of inpatient imaging. There was a significant increase in the inpatient MR imaging RVUs (p = 0.04). No significant trend was found for the aggregated outpatient imaging RVUs. The trends were significant for angiography (p = 0.006), MR imaging (p = 0.002), and sonography (p = 0.04). The aggregated emergency room imaging RVUs showed a significant increase over time (p < 0.03).


CONCLUSION
The number of imaging procedures increased during the study period. There was no overall trend toward increasing use of imaging in inpatients once an adjustment for severity of illness was made. Increases in patient visit-adjusted emergency department use of CT, sonography, and nuclear medicine procedures resulted from changes in practice patterns. For emergency department and outpatient settings, adjusting for the number of patient visits explains a significant portion of the increase in utilization.