How Poor Quality Densitometry Affects Patient Care

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How Poor Quality Densitometry Affects Patient Care

• E. Michael Lewiecki, MD, FACP, FACE
• New Mexico Clinical Research Osteoporosis
  Center
• Albuquerque, NM

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Survey of ISCD Members on DXA Quality

• Online survey sent to 3488 clinicians and 2362
  techs in mid 2006
• Series of questions on quality of DXA studies and
  reports from other facilities
• 743 (21) clinicians and 754 (32) techs
  responded

Lewiecki EM et al. J Clin Densitom.
20069388-392.
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Perceived Frequency of Incorrect DXA Reports
Responses of 690 ISCD clinician members
Lewiecki EM et al. J Clin Densitom.
20069388-392.
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Perceived Impact of Poor Quality DXA Reports on
Patient Care
Responses of 726 ISCD clinician members
Lewiecki EM et al. J Clin Densitom.
20069388-392.
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Implications

• Survey
• Variability in quality of DXA acquisition,
  analysis, and interpretation
• Adverse consequences on patient care
• Possible solutions
• Education and training are likely to improve
  clinical outcomes
• Documentation of proficiency in bone densitometry
  may be a useful quality indicator certification,
  accreditation

Lewiecki EM et al. J Clin Densitom.
20069388-392.
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How can poor quality BMD testing harm patients?
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Categories of Potential Errors

• Pre-testing
• Deciding when to test
• Selecting the right technology
• Testing
• Quality control
• Acquisition
• Analysis
• Post-testing
• Interpretation
• Reporting

Focus adverse clinical consequences
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Mistakes Ordering a BMD Test

• Testing patient when it is unlikely to change
  clinical management
• Misappropriation of limited healthcare resources
• Ex.- DXA on healthy premenopausal woman
• Not testing patient when it is likely to change
  clinical management
• Missed opportunity to identify patient who may
  benefit from therapy
• Ex.- Not doing DXA on 60 year-old man on chronic
  glucocorticoids

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Categories of Indications for BMD Testing

• Population screening
• Testing everyone in a high risk group
• Ex.- women age 65 and older
• Case-finding (risk-based)
• Testing high risk individuals
• Ex.- patient on long-term glucocorticoids
• Treatment-related
• Testing as a baseline or follow-up of treatment
• Ex.- monitoring therapy

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Indications for BMD Testing

• Population screening
• Women aged 65 and older
• Men aged 70 and older
• Case-finding (risk-based)
• Postmenopausal women under age 65 with risk
  factors
• Women during the menopause transition with
  clinical risk factors for fracture, such as low
  body weight, prior fracture or high risk
  medication use
• Men under age 70 with risk factors for fracture
• Adults with a fragility fracture
• Adults with a disease or condition associated
  with low bone mass or bone loss
• Adults taking medications associated with low
  bone mass or bone loss

Baim S et al. J Clin Densitom. 2008 1175-91.
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Indications for BMD Testing

• Treatment-related
• Anyone being considered for pharmacologic therapy
  
• Anyone being treated, to monitor treatment effect
• Anyone not receiving therapy in whom evidence of
  bone loss would lead to treatment
• Women discontinuing estrogen should be
  considered for
  bone density
  testing according to the indications listed above.

Baim S et al. J Clin Densitom. 2008 1175-91.
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Wrong Tool for the Job QUS for Diagnosis

• 66 year-old healthy Caucasian woman has heel QUS
  at shopping mall
• Risk factor mother had hip fracture at age 85
  after a fall
• QUS T-score -1.0
• She is told bone density is normal and that no
  further testing is necessary

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Wrong Tool for the Job QUS for Diagnosis

• Problems
• QUS cannot be used for diagnosis
• QUS T-scores are usually better than DXA
• Possible consequences
• False reassurance
• Underestimation of fracture risk
• Treatment not considered

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FN DXA T-score -2.3 with 27 10-year
probability of major osteoporotic fracture meets
NOF guideline for drug therapy
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Wrong Tool for the JobQCT for Diagnosis

• 73 year-old Hispanic woman has QCT of spine
• No clinical risk factors for fracture
• QCT T-score -2.5
• She is told she has osteoporosis and prescribed
  alendronate

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Wrong Tool for the JobQCT for Diagnosis

• Problems
• QCT cannot be used for diagnosis
• QCT T-scores are usually worse than DXA
• Possible consequences
• Diagnosis may be incorrect
• Overestimation of fracture risk
• Unnecessary treatment may be given

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FN DXA T-score -1.8 with low probability of
osteoporotic fractures does not meet NOF
guideline for drug therapy
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Non-central DXA Devices

• T-scores from measurements other than DXA at the
  femur neck, total femur, lumbar spine, or
  one-third (33) radius cannot be used according
  to the WHO diagnostic classification because
  those T-score are not equivalent to T-scores
  derived by DXA

Baim S et al. J Clin Densitom. 2008 1175-91.
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BMD Testing Technologies
LS, FN, TH, 33R 33R FN
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Quality Control Assessment of Instrument
Calibration

• Methods
• Do periodic phantom scans
• Plot and review calibration data
• Take corrective action when necessary
• Non-compliance may cause BMD measurement to be
  higher or lower than actual
• Consequences are possible errors in
• Diagnostic classification
• Assessment of fracture risk
• Treatment decisions

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Quality Control ChartNormal Calibration
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Quality Control ChartCalibration Drift
Example Aging of equipment, local environmental
changes
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Quality Control ChartCalibration Shift
Example Replacement of major component, moving
instrument
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Quality Control Precision Assessment

• Method 2 or more scans on series of patients to
  determine reproducibility of BMD measurements
• Without precision assessment, it cannot be known
  whether an apparent BMD change is real or a
  measurement error
• If insignificant BMD changes are reported as
  real, then
• Harmful or expensive treatment decisions
• Unnecessary or expensive referral or testing

Assessment of technologist calibration
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Precision Assessment

• Each DXA facility should determine its precision
  error and calculate the LSC
• The precision error supplied by the manufacturer
  should not be used
• Every technologist should perform an in vivo
  precision assessment using patients
  representative of the clinics patient population

Baim S et al. J Clin Densitom. 2008 1175-91.
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Quality Control Standard Operating Procedures
(SOPs)

• Reference manual for operating a bone
  densitometry facility
• Often includes
• Procedures for radiation safety
• Documentation of regulatory compliance
• Instrument calibration assessment and monitoring
• Staff training standards and documentation
• Routine for patient scheduling and education
• Precision assessment standards
• Facility procedures for measuring additional
  skeletal sites and doing VFA
• Much more

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Acquisition Mistakes

• Incorrect demographic information
• Improper patient positioning
• Removable artifacts not removed
• Wrong scan mode
• Invalid skeletal site
• Fat panniculus issues

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Poor Hip Position- Abducted
Faxed Image
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Study of BMD with Femur Angulation using
Bilateral Foot Positioner

• 200 patients had bilateral hip BMD on GE Lunar
  Prodigy using bilateral foot positioner
• 85 of patients had femur angles ? 6
• No correlation between femur angles and left to
  right BMD differences
• Small degrees of angulation may not significantly
  affect hip BMD

7 Abduction
4 Adduction
Wong JC et al. J Clin Densitom. 20058472-475.
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Differences in Leg Rotation
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Study on Effect of Leg Rotation on Hip BMD

• 50 women volunteers in Sri Lanka tested on
  Norland Eclipe XR with customary leg rotation,
  10 excess internal rotation, and 10 excess
  external rotation
• Excess internal rotation decreased BMD mean
  0.009 at FN (P lt0.001), gt LSC at FN in 12 of
  patients
• Excess external rotation increased BMD mean
  0.005 (P 0.119), gt LSC at FN in 8
• Malrotation may be a confounding factor in
  interpreting serial BMD tests

Lekamwasam S et al. J Clin Densitom.
20036331-336.
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Poor Spine Position- Tilted
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Tablets (calcium, multivitamin) in Pocket
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Chromium Tablets
Baseline
Next Day
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Study of Effect of Calcium Tablets on Lumbar
Spine BMD

• Phantoms and volunteers tested with calcium tabs
  over lying bone, soft tissue, or both, using 3
  different models of Hologic instruments
• Single tablet had little effect on L1L4 BMD
• Substantial effect on BMD of single vertebral
  body (as much as 12.6 increase)
• Undissolved calcium tablet may alter diagnostic
  classification and precision if fewer than 4
  vertebral bodies analyzed

Kendler DL et al. J Clin Densitom. 2006997-104.
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Study on Effect of Common Artifacts on Lumbar
Spine BMD

• Cadaver study with high BMD and low BMD spines
  using variety of artifacts with Hologic Discovery
  W
• Bra wires and calcium tablets affected BMD for
  low BMD spine
• GB clips and gallstone had no effect on either
  spine
• No artifacts affected BMD for high BMD spine

Morgan SL et al. J Clin Densitom. 200811243-249.
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Scan Mode Makes a Difference Same Obese Patient
(BMI 36.6), Different SMs (Hologic)
Array Mode (60 sec.) L1-L4 BMD
0.034 g/cm2 (gtLSC)
Fast Array Mode (30 sec.) L1-L4 BMD 0.829 g/cm2
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Fat Panniculus
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Analysis Mistakes

• Analyzing structurally abnormal bones
• Poor identification of bone edges
• Mislabeling of vertebral bodies
• Poor placement of ROI

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Severe Scoliosis
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Structural Abnormality
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Poor Neck Box Placement
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Case Study

• 65 year-old man has osteoporosis (L1-L4 T-score
  -3.3) associated with hypogonadism
• Treatment with alendronate resulted in a
  significant BMD increase at L1-L4, but a
  subsequent DXA showed a significant BMD loss
• He is referred for evaluation of non-response to
  therapy
• What do you do?

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What do you do?

• Change therapy to an injectable bisphosphonate
• Stop alendronate and start teriparatide
• Order lab studies to evaluate for factors
  contributing to bone loss
• Other

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Lumbar Spine Scans
Baseline L1-L4 0.729 g/cm2
Follow-up 1 0.038 (5.3)
Follow-up 2 -0.037 (-5.1)
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Diagnosis

• Mislabeled vertebral bodies
• Re-analysis of last study with correctly labeled
  vertebral bodies showed stable BMD since the
  previous study, representing a good response to
  therapy
• Recommendation no change in therapy

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Interpretation Errors

• Misapplication of guidelines, standards, tools
• WHO diagnostic criteria
• FRAX
• NOF intervention thresholds
• ISCD Official Positions
• Invalid comparison of serial DXA studies

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Good Report or Bad Report?

• Actual report
• L-spine measurements range from T score of -1.6
  at L2 to -1.4 at L4
• Left hip measurements range from T score of -2.7
  for Wards triangle to -1.2 at trochanter
• Impression osteoporosis of left hip, osteopenia
  of spine
• Bad report
• Wrong diagnosis Dont use Wards area
• Dont cherry pick vertebral bodies
• Dont make more than one diagnosis
• Should be T-score not T score

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Good Report or Bad Report?

• Actual report
• 62 year-old Asian woman with FN T-score -2.6
  woman has been on alendronate for 8 years
• Based on FRAX, the 10-year probability of major
  osteoporotic fracture is 9.1 and 1.8 for hip
  fracture
• Bad report
• FRAX does not apply to treated patients

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Good Report or Bad Report?

• Actual report
• 82 year-old Black male smoker has FN T-score
  -2.3
• FRAX shows a 10 hip fracture risk of 3.0
• Treatment is indicated according to the NOF Guide
  
• Bad report
• FRAX Patch not used to convert T-score
• Repeat calculation with FRAX Patch shows that
  treatment not indicated with NOF guide

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73 Year-old Woman Referred for Bone Loss
11/19/01
10/17/02
FN BMD 0.626
FN BMD 0.581
Reported bone loss 0.045 (7.2)
Problems Invalid comparison of left hip with
right hip different instruments
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Potential Missed Diagnosis Metastatic Prostate
Carcinoma
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Premenopausal Woman with Low BMD

• Healthy premenopausal 29 year-old female dentist
  with no history of fractures
• Free heel QUS at health fair shows T-score -1.2
• Physician orders DXA that shows L1-L4 T-score
  -2.5
• Osteoporosis is diagnosed and she is started on
  alendronate
• Three years later she applies for disability
  insurance

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Economic Consequences Premenopausal Woman

• Disability insurance coverage is denied due to
  diagnosis of osteoporosis
• Evaluation by a consulting physician concludes
  that she does not meet criteria for a diagnosis
  of osteoporosis and that fracture risk is low
• Alendronate is stopped and a letter of
  explanation is sent to insurance company
• With reconsideration, insurance is again denied

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ISCD Official Positions

• Benefits
• Standardization of testing methodologies
• Very helpful in clinical practice
• Focus attention on areas in need of study
• Limitations
• Evidence often limited
• Applicability may vary by location

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FRAX

• Benefits
• Quantitative assessment of fracture risk
• Greater clinical utility than RR
• Limitations
• BMD input is FN only
• Dose-effect of risk factors not considered
• Important risk factors not included
• Limited to certain ethnicities in USA
• May over- or under-estimate actual fracture risk
• Does not apply to treated patients
• Website inconsistent and inconvenient

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NOF Guide

• Benefits
• Improved patient selection for treatment
• Expanded applicable population
• Better use of limited healthcare resources
• Limitations
• Based on numerous assumptions
• Apparent internal conflicts
• May identify some patients for treatment when
  little or no evidence of benefit (T-score gt -1.5)

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Summary

• Poor quality bone densitometry is common
• Consequences include inappropriate patient
  management decisions, poor clinical outcomes, and
  unnecessary healthcare expenses
• Thorough understanding of technological
  standards, fracture risk assessment, and
  treatment guidelines is necessary for good
  quality control, acquisition, analysis,
  interpretation, and reporting
• Education and training are pathways to improving
  quality
• Certification and accreditation may provide
  assurance of quality