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. Author manuscript; available in PMC: 2010 May 25.
Published in final edited form as: Arch Intern Med. 2009 May 25;169(10):972–981. doi: 10.1001/archinternmed.2009.78

Table 3.

Rapidity and modality of imaging for Medicare patients with acute low back pain and the individual and practice characteristics of their primary care physiciansa

Characteristics N (%)
Total = 35,039
Adjusted
Odds Ratiob
(95% CI)
Adjusted
Odds Ratiob
(95% CI)
Characteristics of Patients
Age
 65-74 19,856 (56.7) 1.00 1.00
 75-84 12,345 (35.2) 1.10 (1.02-1.18)a 1.07 (1.01-1.14)a
 >84 2,838 (8.1) 1.02 (0.89-1.17) 0.96 (0.85-1.09)
Male 24,281 (69.3) 1.00 1.00
Female 10,758 (30.7) 1.04 (0.96-1.13) 1.04 (0.96-1.13)
Race
 White 30,746 (87.8) 1.00 1.00
 Black 2,626 (7.5) 0.84 (0.75-0.95)b 0.88 (0.78-0.99)a
 Other 1,667 (4.8) 0.70 (0.53-0.93)a 0.72 (0.52-0.94)b
Not Medicaid eligible 30,664 (87.5) 1.00 1.00
Medicaid eligible 4,375 (12.5) 0.80 (0.67-0.94)b 0.79 (0.66-0.94)b
Klabunde score (mean) 35,039 (100) 1.09 (1.02-1.17)b 1.09 (1.02-1.16)a
Charlson index
 No comorbidities 31,684 (90.4) 1.00 1.00
 1 comorbidity 1,711 (4.9) 1.16 (0.97-1.38) 1.21 (1.03-1.42)a
 ≥2 comorbidities 1,644 (4.7) 0.90 (0.73-1.11) 0.92 (0.73-1.15)
Median household income in patient’s
zip code
 Above county median 17,693 (50.5) 1.00 1.00
 Below county median 16,599 (47.5) 1.00 (0.92-1.10) 0.93 (0.86-0.99)a

Characteristics of the PCP and his or
her practice
Specialty
 General internal medicine 16,835 (48.0) 1.00 1.00
 Family/general practice 18,204 (52.0) 0.92 (0.86-0.99)a 0.93 (0.86-1.00)a
Years in practice
 0-10 9,452 (27.0) 1.00 1.00
 11-20 12,574 (35.9) 0.99 (0.92-1.08) 0.99 (0.92-1.07)
 >20 13,013 (37.1) 0.99 (0.90-1.09) 1.00 (0.90-1.10)
Board certified 30,640 (87.5) 1.00 1.00
Not board certified 4,320 (12.3) 0.99 (0.86-1.14) 0.97 (0.84-1.12)
Medical school outside U.S./Canada 5,958 (17.0) 1.00 1.00
U.S./Canadian medical school 29,071 (83.0) 1.03 (0.93-1.14) 1.05 (0.96-1.15)
Practice type
 Solo/2-person 15,452 (44.1) 1.00 1.00
 Small group, 3-10 7,104 (20.3) 1.11 (0.97-1.26) 1.07 (0.94-1.22)
 Medium group, 11-50 2,877 (8.2) 1.50 (1.28-1.77)c 1.37 (1.19-1.58)c
 Large group, >50 1,366 (3.9) 1.24 (1.01-1.53)a 1.21 (1.02-1.44)a
 Medical school 822 (2.4) 0.93 (0.72-1.20) 0.91 (0.72-1.16)
 Hospital practice/Other 6,889 (19.7) 1.02 (0.89-1.17) 1.02 (0.90-1.15)
 Group/staff HMO 529 (1.5) 0.97 (0.73-1.29) 1.01 (0.76-1.36)
Practice revenue derived from Medicaid
 0-5% 17,824 (50.9) 1.00 1.00
 6-15% 10,908 (31.1) 0.92 (0.84-1.00)a 0.92 (0.85-1.00)a
 >15% 6,307 (18.0) 0.84 (0.76-0.93)c 0.85 (0.77-0.94)c
Practice revenue derived from capitation
 None 16,659 (47.5) 1.00 1.00
 1-10% 7,489 (21.4) 1.00 (0.83-1.07) 0.99 (0.93-1.06)
 11-25% 4,330 (12.4) 1.08 (0.95-1.23) 1.07 (0.95-1.21)
 >25% 6,561 (18.7) 0.93 (0.83-1.03) 0.89 (0.81-0.98)a
Practice ownership
 Full owner 14,830 (42.3) 1.00 1.00
 Part-owner 9,298 (26.5) 0.88 (0.90-0.97)b 0.89 (0.90-0.98)a
 Employed 10,911 (31.1) 0.80 (0.70-0.93)b 0.82 (0.71-0.95)b
Financial incentives
 None of three types of incentives 2,828 (8.1) 1.00 1.00
 Only clinical quality incentives 63 (0.2) 0.73 (0.43-1.25) 0.62 (0.39-1.01)
 Only patient satisfaction incentives 122 (0.4) 3.41 (2.70-4.30)c 2.63 (2.12-3.26)c
 Only productivity incentives 13,240 (37.8) 0.97 (0.87-1.09) 0.97 (0.87-1.09)
 Clinical quality and patient
  satisfaction, but not productivity
  incentives
144 (0.4) 0.70 (0.52-0.95)a 0.75 (0.54-1.04)
 Clinical quality and productivity, but
  not patient satisfaction incentives
1,005 (2.9) 1.01 (0.87-1.17) 1.01 (0.87-1.16)
 Productivity and patient satisfaction
  incentives, but not clinical quality
  incentives
2,128 (6.1) 0.99 (0.85-1.15) 0.97 (0.83-1.14)
 All three types of incentives 3,200 (9.1) 0.86 (0.73-1.02) 0.89 (0.76-1.03)
 Not asked questions on specific
  incentives
11,902 (34.0) 1.07 (0.90-1.28) 1.05 (0.88-1.26)
a

Unweighted counts, weighted percentages, and odds ratios are based on analysis of fee-for-service Medicare claims from 2000-2002 and 2004-2006 for 35,039 fee-for-service Medicare beneficiaries treated by one of 4,567 Community Tracking Study primary care physicians.

b

CI denotes confidence interval. Adjusted for beneficiary age, sex, Medicaid eligibility, race, and Klabunde and Charlson comorbidity scores; median household income in the beneficiary’s zip code and percentage of adults 25 years or older with at least 12 years of education; the CTS PCP’s specialty, number of years in practice, board certification status, site of medical school, practice ownership status, and exposure to financial incentives based on performance on quality, profiling, patient satisfaction, or productivity; type and size of the CTS PCP’s practice, as well as the percentage of its revenues derived from Medicare, Medicaid, and capitation; urban vs. rural location; radiologist supply per 1,000 capita in the CTS PCP’s county; the round of the survey (2000-2001 or 2004-2005), and the sampling cluster for the CTS survey (site dummy).