Table 1.

Summary of Patient Characteristics and Low Back Magnetic Resonance Imaging (MRI) Utilization

	(1) Physician Self-Referral Status			(2) Among Self-Referring Physicians
	Traditional MRI Users	Will or Has Acquired MRI	p-Value	Before MRI Acquisition	After MRI Acquisition	p-Value
Orthopedist episodes (n = 78,914)	70,400	8,514		3,485	5,029
Orthopedic surgeons (n)	7,717	1,271
Patient characteristics
Female (%)	64.4	65.3	0.118	64.5	65.8	0.228
Black (%)	4.6	4.3	0.119	4.4	4.2	0.743
Mean age (years)	76.5	76.4	0.077	76.5	76.3	0.098
With dual Medicaid coverage (%)	8.4	7.0	<0.001	7.3	6.7	0.355
Mean prior year total Medicare spending (U.S.$)	5,093	4,883	0.052	4,726	4,992	0.163
Receives low back MRI within 180 days (%)	19.5	25.0	<0.001	21.8	27.2	<0.001
Primary care episodes (n = 661,553)	655,393	6,160		2,559	3,601
Primary care physicians (n)	84,809	1,033
Patient characteristics
Female (%)	64.9	65.7	0.183	66.1	65.4	0.542
Black (%)	5.9	3.8	<0.001	3.9	3.7	0.748
Mean age (years)	76.5	76.5	0.523	76.6	76.5	0.588
With dual Medicaid coverage (%)	15.4	11.7	<0.001	12.1	11.5	0.487
Mean prior year total Medicare spending (U.S.$)	4,131	4,332	0.077	4,054	4,529	0.048
Receives low back MRI within 180 days (%)	10.5	14.5	<0.001	11.2	16.7	<0.001