Background: The objective of this study was to examine variations in MRI/CT utilization between family physicians (FPs) and general internists (IMs) within a multi-specialty group practice.
Material/Methods: Using administrative data, we computed ordering rates of MRI/CT per 1,000 outpatient clinic visits and per 1,000 unique patients and rate ratios (RR) to compare rates between 34 FPs and 24 IMs practicing in 7 clinics located within 50 miles of the radiology facility. We also assessed intra-specialty variation. Sources and degree of variation were determined separately for FPs and IMs through multivariate linear regression modeling.
Results: The IMs ordered MRI/CTs at twice the rate of FPs (29.6 vs. 14.8 per 1,000). Although the absolute ranges by specialty were statistically similar, the variance was signifi cantly higher for IMs (86.1
vs. 52.3; p

Keywords: Ambulatory Care - utilization, Group Practice - statistics & numerical data, Internal Medicine - statistics & numerical data, Magnetic Resonance Imaging - utilization, Physicians, Family - statistics & numerical data, Tomography, X-Ray Computed - utilization, Ambulatory Care - utilization, Data Collection, Group Practice - statistics & numerical data, Health Services - utilization, Internal Medicine - statistics & numerical data, Linear Models, Magnetic Resonance Imaging - utilization, Physician's Practice Patterns - statistics & numerical data, Physicians, Family - statistics & numerical data, Professional Practice - statistics & numerical data, Regression Analysis, Severity of Illness Index, Texas, Tomography, X-Ray Computed - utilization