Intensity of Imaging for Low Back Pain in Elderly Patients

AcademyHealth Annual MeetingJune 2007

HH Pham, MD, MPH, D Schrag, MD, MPH

C Corey, MS, J Reschovsky, PhD

HR Rubin, MD, PhD, BE Landon, MD, MBA

Background

Medicare spending on imaging services has increased dramatically since 2000 with unclear clinical benefits for beneficiaries

Guidelines allow discretion for imaging of elderly patients with acute low back pain

Little representative data on non-clinical factors associated with intensity of imaging

Research questions

What physician, practice, market, and non-clinical patient factors are associated with more intensive imaging for acute low back pain?

Does the economic environment in which physicians practice influence discretionary use of imaging?

Data sources (1)

2000-2001 Community Tracking Study Physician Survey• Nationally representative, clustered in 60 communities• Non-federal, completed training, 20+ hrs of clinical care/week• 12,406 respondents, ~50% PCPs• 59% response rate

Questions• Specialty, board certification, FMG status• Practice type, revenue sources (Medicaid, Medicare), capitation• Ability to obtain specialist and imaging referrals• Overall effect of financial incentives (increase/decrease services)• Compensation based on quality, profiling, patient satisfaction• Practice ownership

Data sources (2)

Complete 2000-2002 Medicare claims for 1.09 million beneficiaries seen by CTS physicians in year 2000

Geographic data from Area Resources File on number of patient care radiologists per capita, household income, and education levels

Design and Analysis

Back pain diagnosis identified for year 2001 Followed for 6 months after back pain diagnosis Modeled “intensity” of imaging

• never imaged imaged 29 -180 days imaged within 28 days• “Intensity” measured for:

- (a) any imaging modality; and (b) only CT/MRI

Excluded patients diagnosed by a radiologist Adjusted for comorbidities during year 2000, physician,

practice, and area factors (site fixed effects) Repeated analyses, excluding patients with visits to

other physicians between diagnosis and imaging dates

63,075 (15%) patients of 318,148 linked to a CTS PCP and had a diagnosis of acute low back pain in 2001

24,515 (39%) meeting clinical inclusion criteria (no potential indications for imaging 6 months prior to LBP diagnosis or

between diagnosis and imaging dates

5,964 (28%) imaged within 28 days

5,330 (90%) by XR725 (12%) by CT/MRI

15,011 (67%) never imaged

1,017 (4%) imaged between 29-180 days734 (73%) by XR

314 (31%) by CT/MRI

21,992 (89%) meeting inclusion criteria and not diagnosed by a radiologist

Study population

Clinical exclusions

Modified NCQA’s measure of inappropriate imaging for acute LBP

Cancers* Neurologic deficits* Trauma,* falls, injury Infections – endocarditis, osteomyelitis, TB, etc. IV drug use* Anemia – not hereditary, Fe deficiency, or blood loss Constitutional symptoms – weight loss, fever, night

sweats, fatigue/malaise, loss of appetite

Care relationships between acute LBP patients and their plurality PCP

Median (IQR) % of E&M visits with PCP 63 (47-80)

Had a visit with their CTS PCP within 6 months of LBP diagnosis 81%

Diagnosed by their CTS PCP 52%

Diagnosed in their CTS PCP’s practice 60%

Diagnosed by any PCP

Specialties of other diagnosing clinicians (outside of their CTS PCP’s practice)

62%

Orthopedic surgeon 9%

Chiropractor 15%

Site of imaging studies performed within 28 days of diagnosis

Modality

Total imaged

N

Patients imaged in

PCP’s practice

N (%)

Any 6,981 2,439 (37.5)

X-Ray 6,064 2,192 (38.9)

CT or MRI 1,039 280 (27.1)

Timing of imaging after LBP diagnosis

Imaging procedure

Patients, N

Number of days between diagnosis and imaging,

Median (IQR)

Any modality 6,981 0 (0-7)

CT 165 9 (3-35)

MRI 879 13 (4-36)

Predictors of intensity of imagingPatient factors and radiologist supply

Characteristic

Any modality

Adjusted OR (95% CI)

CT or MRI

Adjusted OR (95% CI)

Female 1.01 (0.92-1.11) 0.81 (0.67-0.96)*

Medicaid eligible 0.81 (0.70-0.94)* 0.94 (0.71-1.25)

Race (vs. white)

Black 0.83 (0.77-0.96)* 0.67 (0.46-0.99)*

Other 0.95 (0.71-1.26) 0.91 (0.58-1.42)

Radiologists/1000 (vs. lowest quartile)

Highest quartile 1.10 (0.97-1.25) 1.31 (1.02-1.69)*

No effect for median household income in the patient zip code; % adults with 12+ yrs of education in the county; or Klabunde or Charlson scores

Predictors of intensity of imagingPhysician factors

Characteristic

Any modality

Adjusted OR (95% CI)

CT or MRI

Adjusted OR (95% CI)

FP/GP specialty (vs. IM) 0.95 (0.87-1.03) 0.83 (0.67-1.02)

Effect of incentives (vs. increase services)

To reduce services 0.83 (0.68-1.01) 0.73 (0.51-1.00)*

No effect on services 1.03 (0.94-1.12) 1.00 (0.80-1.25)

No effect for years in practice; board certification; IMG status; compensation based on productivity, quality, profiling or

patient satisfaction measures, or practice ownership

Predictors of intensity of imagingPractice factors

Characteristic

Any modality

Adjusted OR (95% CI)

CT or MRI

Adjusted OR (95% CI)

% Revenue from capitation (vs. none)

1-10% 1.05 (0.94-1.17) 0.84 (0.68-1.03)

11-25% 0.98 (0.85-1.13) 0.74 (0.54-1.00)*

>25% 0.94 (0.79-1.12) 0.67 (0.50-0.90)**

Practice type (vs. solo/2)

Small group (3-10) 1.19 (1.03-1.37)* 1.10 (0.79-1.52)

Medium group (11-50) 1.49 (1.21-1.84)*** 0.94 (0.58-1.50)

Large group (>50) 1.22 (1.00-1.49)* 1.29 (0.85-1.96)

Medical school 0.84 (0.62-1.14) 0.64 (0.29-1.43)

No consistent effect for revenue from managed care, Medicare, or Medicaid

Limitations

No certainty regarding appropriateness of imaging• Not benchmarking – only comparing relative performance• Unlikely systematic under-coding of exclusions by physician or

practice characteristics, or by white patient race and higher SES• Uncertainty is comparable to claims-based measures of underuse

Lack data on presence of imaging equipment in practices

Cannot identify physician(s) responsible for referrals• For imaging or to specialists• But consistent relationships between characteristics of the CTS

PCP and intensity of imaging

Conclusions

Substantial minority of elderly patients with uncomplicated LBP are imaged early, often in their physician’s practice• Most cases of rapid imaging use XR’s, not CT/MRI

Overall financial incentives matter, but no association with specific types of performance-based compensation

Subgroups of patients who tend to receive fewer services may sometimes benefit

Incentives to increase or decrease services may have mixed effects on quality that may go undetected if the majority of performance metrics reflect underuse

Geographic variation in percent of patients imaged within 28 days

Before exclusions

After clinical exclusions

Any Modality

After clinical exclusions

CT/MRI

CTS Market Unadjusted % Unadjusted % Adjusted % Unadjusted % Adjusted %

Seattle 22.6 20.7 29.2 2.6 4.7

Phoenix 24.6 23.9 28.9 2.9 4.6

Miami 34.0 26.3 21.5 5.9 3.5

Newark 32.3 27.4 27.5 7.6 4.9

Cleveland 29.7 27.5 29.3 4.5 5.0

Indianapolis 29.5 28.5 28.3 5.8 4.9

Lansing 27.3 28.5 28.9 3.3 5.1

Greenville 30.0 29.8 28.4 4.6 4.6

Little Rock 29.0 30.4 29.3 6.6 5.2

Orange Cty 28.1 30.9 26.6 5.0 4.7

Boston 29.5 31.8 29.4 11.1 5.8

Syracuse 31.6 33.3 30.5 4.9 5.3