Geographic variation and trends in carotid imaging among medicare beneficiaries, 2001 to 2006.

BACKGROUND Diagnostic imaging among Medicare beneficiaries is an important contributor to rising health care costs. We examined temporal trends and geographic variation in the use of carotid ultrasound, carotid magnetic resonance angiography (MRA), and carotid x-ray angiography. METHODS AND RESULTS Analysis of a 5% national sample of claims from the Centers for Medicare and Medicaid Services for 1999 through 2006. Patients were 65 years or older and underwent carotid ultrasound, carotid MRA, carotid x-ray angiography, or a carotid intervention. The main outcome measures were annual age-adjusted rates of carotid imaging and interventions and factors associated with the use of carotid imaging. Rates of imaging increased by 27%, from 98.2 per 1000 person-years in 2001 to 124.3 per 1000 in 2006. Rates of carotid ultrasound increased by 23%, and rates of MRA increased by 66%. Carotid intervention rates decreased from 3.6 per 1000 person-years in 2001 to 3.1 per 1000 person-years in 2006. In 2006, rates of carotid ultrasound were lowest in the New England, Mountain, and West North Central regions and highest in the Middle Atlantic and South Atlantic regions. Regional differences persisted after adjustment for patient demographic characteristics, history of vascular disease and other comorbid conditions, and study year. CONCLUSIONS From 2001 through 2006, there was substantial growth and variation in the use of carotid imaging, including a marked increase in the use of MRA, and a decrease in the overall rate of carotid intervention.