Determinants of diagnostic imaging utilization in primary care

To examine patient and physician factors affecting utilization of diagnostic imaging in primary care.

Patient-level data from a large academic group practice over the period July 1, 2007, through June 30, 2009.

This is a retrospective cohort study of 85,277 patients cared for by 148 primary care physicians (PCPs). The dependent variable is the number of outpatient imaging exams ordered by each patient's PCP over the study period. Independent variables include 17 patient factors describing both clinical need and demographic characteristics and 7 physician factors.

Data were collected from the electronic medical record and associated administrative databases.

Patient factors having a statistically significant effect on both the probability race, more than 10 medications, congestive heart failure, diabetes, hypertension, other problems, visits to the PCP, visits to specialists, and imaging exams ordered by specialists. For physician factors, experience, gender, and having another degree were statistically significant in both portions of the model.

Both patient and physician factors have a substantial effect on primary care outpatient diagnostic imaging utilization. Several of these significantly influence both the probability that any images will be ordered and the intensity (number) of imaging.