Utilization of diagnostic medical imaging: comparison of radiologist referral versus same-specialty referral

To retrospectively compare the frequency with which patients underwent diagnostic medical imaging procedures during episodes of outpatient medical care according to whether their physicians referred patients for imaging to themselves and/or physicians in their same specialty or to radiologists.

Institutional review board approval was not necessary for this HIPAA-compliant study. An insurance claims database from a large national employer-based health plan was obtained. Claims data from 1999-2003 were grouped into episodes of care for six conditions: cardiopulmonary disease, coronary and/or cardiac disease, extremity fracture, knee pain, intraabdominal malignancy, and stroke. For each condition, each referring physician's behavior was categorized as either "same-specialty referral" or "radiologist referral" on the basis of that physician's entire history of imaging referrals for the condition. The frequency with which patients underwent diagnostic medical imaging procedures during episodes of care was compared according to whether their physicians referred patients for imaging to themselves and/or same-specialty physicians or to radiologists. Rates were compared by using chi(2) tests, and logistic regression was used to compare utilization rates, with patient age and number of comorbidities as covariates.

For the conditions evaluated, physicians who referred patients to themselves or to other same-specialty physicians for diagnostic imaging used imaging between 1.12 and 2.29 times as often, per episode of care, as physicians who referred patients to radiologists (P < .005 for all comparisons). Adjusting for patient age and comorbidity, the likelihood of imaging was 1.196-3.228 times greater for patients cared forby same-specialty-referring physicians.

Same-specialty-referring physicians tend to utilize imaging more frequently than do physicians who refer their patients to radiologists. These results cannot be explained by differences in case mix (because analyses were performed within six specific conditions of interest), patient age, or comorbidity.