The effect of financial incentives on the volume of diagnostic imaging ordered by physicians
- Presenter:
Chair: Richard C. Lindrooth; Discussant: TBA Tue June 6, 2006 13:45-15:15 Room 225
Rationale: Medical imaging is a large component of health care costs in the United States, with an estimated annual cost almost $100 billion, and has one of the fastest growth rates (approximately 10% per year) among all medical services. Imaging is usually provided through physician referral, and therefore, may be influenced by financial incentives faced by the referring physician.
In this study, we analyze the differences in imaging utilization between self-referring and radiologist-referring physicians, while controlling for patient characteristics and diagnoses. If a patient has an office visit and a subsequent related image, and the same physician bills for both events, the physician is identified as a self-referrer with a financial interest in the imaging procedure to which he or she refers the patient. If the image is performed by a radiologist, then the referring physician is flagged as having no financial interest in the referral. (Referrals to physicians other than radiologists are analyzed as a separate category because the incentives are unclear.)
Objective: To measure the effect of physician financial incentives, as captured by self- versus radiologist-referral, on the utilization of imaging studies, controlling for patient demographics and co-morbidities, geographic location, practice setting (physician office, outpatient hospital, or inpatient hospital), and other physician-related factors.
Methods: We use claims data from a large national employer plan for five years (1999-2003). We identify patients with certain conditions such as acute upper respiratory tract symptoms, headache, and knee pain. We construct episodes of care and for each episode, observe whether an image was ordered, the type of image, total imaging costs, and total patient care costs. Each medical condition is analyzed indepently. Outcomes of interest for each patient are (a) percent of episodes with imaging, (b) total costs of imaging, and (c) total medical costs, with costs measured in measured in global relative value units (RVUs) to control for price differences. Logit regression is used to analyze outcome (a) and log-linear regression for outcomes (b) and (c).
Preliminary Results: For cardiac imaging the number of images per patient is higher when the treating physician does his/her own imaging than when the patient is referred to a radiologist (2.8 ultrasounds and 2.9 nuclear medicine images per patient by self-referrers versus 2.6 and 2.7 respectively for radiologist-referrers). But the number of images per patient is even larger when patients are referred to an independent clinic (2.9 ultrasounds and 3 nuclear medicine procedures), and the financial motivations are unclear. Controlling for patient and neighborhood characteristics, and state physician supply, physicians who performed their own imaging for heart disease performed 6% more images than physicians who sent the patient to a different physician.
Conclusions: There is some evidence that imaging utilization is higher if a physician self-refers patients than if the patient is referred to a radiologist or a different physician. Analysis of costs of imaging may reveal sharper differences between self-referring and radiologist-referring physicians. The results of this study will assist policy makers and payers in designing effective incentive structures to ensure appropriate utilization.
