Pulmonary Embolism Pulmonary Embolism DiagnosisDiagnosis

Physician Utilization Patterns of Computed Tomography (CT) Physician Utilization Patterns of Computed Tomography (CT) and Ventilation-Perfusion (V/Q) scans in the Diagnosis of and Ventilation-Perfusion (V/Q) scans in the Diagnosis of

Suspected Pulmonary Embolism (PE) in Inpatients and the Suspected Pulmonary Embolism (PE) in Inpatients and the Emergency Department: A Prospective Observational StudyEmergency Department: A Prospective Observational Study

Tom Scott, MD

Georgetown University

The ProblemThe Problem

PE’s are common – 600,000 per yearPE’s are common – 600,000 per year If diagnosed, they are rarely fatal and rarely recurIf diagnosed, they are rarely fatal and rarely recur If not diagnosed, they are commonly leathal (15-If not diagnosed, they are commonly leathal (15-

30%)30%) Symptoms are very non-specificSymptoms are very non-specific There is no commonly accepted diagnostic There is no commonly accepted diagnostic

algorithmalgorithm A 2003 NEJM review suggests V/Q and CT A 2003 NEJM review suggests V/Q and CT

are equally appropriate as first line tests, are equally appropriate as first line tests, regardless of pre-test probability for PE*regardless of pre-test probability for PE*Fedullo P. F., Tapson V. F. The Evaluation of a Suspected Pulmonary Emboism. N Engl J Med 2003; 349:1247-1256.

Patient suspected of PEInpatients and ED

CT or V/Q scan ordered

Physician participation requested

Pre-Test survey Pre-test probability for PE based on 2 validated clinical models:

• Wells Criteria•PIOPED

V/Q or CT scan

administered

Post-Test Survey • Comparison of utility CT and V/Q scan in PE diagnosis• Analyze the use of D-Dimer in low-pre-test probability patients

Schematic Diagram of Study Design

M-F 9am-6pm

Clinical Models to Assess Clinical Models to Assess PE RiskPE Risk

Wells Criteria – Both objective clinical data and subjective Wells Criteria – Both objective clinical data and subjective clinician impressionclinician impression

PE Incidence: Low - 3.6%; Intermediate – 20.5%; High – 66.7%PE Incidence: Low - 3.6%; Intermediate – 20.5%; High – 66.7%

Fedullo P. F., Tapson V. F. The Evaluation of a Suspected Pulmonary Emboism. N Engl J Med 2003; 349:1247-1256.

Clinical Models to Assess Clinical Models to Assess PE RiskPE Risk

PIOPED Criteria – Correlates well with incidence of PEPIOPED Criteria – Correlates well with incidence of PE Based entirely of clinician impression, not clinical risk factorsBased entirely of clinician impression, not clinical risk factors

Pretest Clinical Pretest Clinical Gestalt of PE Gestalt of PE Probability Probability

Actual PE Rate on Actual PE Rate on PA AngiogramPA Angiogram

Low (“<20%” should Low (“<20%” should have PE) have PE)

9% 9%

Intermediate (“20-Intermediate (“20-79%” should have 79%” should have

PE) PE)

30% 30%

High (“80-100%” High (“80-100%” should have PE) should have PE)

68% 68% PIOPED Investigators. JAMA 1990; 263: 2753-2759.

Primary End PointsPrimary End Points

Compare CT and V/Q scans based onCompare CT and V/Q scans based on % Non-Diagnostic Studies% Non-Diagnostic Studies PE diagnostic ratePE diagnostic rate Incidence of an alternate diagnosis (non-PE) not Incidence of an alternate diagnosis (non-PE) not

apparent on chest X-rayapparent on chest X-ray Subjective changes in patient management or Subjective changes in patient management or

treatment.treatment. D-Dimer use in low pre-test probability patientsD-Dimer use in low pre-test probability patients

% of low prob patients with D-Dimer% of low prob patients with D-Dimer % of patients with negative D-Dimer% of patients with negative D-Dimer Cost ImplicationsCost Implications

Patient CharacteristicsPatient Characteristics

## %% ## %%TotalTotal 144144 100%100% 1515 10%10%Mean Mean

AgeAge54.754.7 -------------- 60.560.5 --------------

FemaleFemale 8787 60%60% 1010 11%11%African African AmericAmeric

anan

5858 40%40% 66 10%10%

WhiteWhite 7575 50%50% 99 12%12%All All

OthersOthers1111 8%8% 00 0%0%

All PatientsAll Patients PE+PE+

Race

Patient CharacteristicsPatient Characteristics

## %% ## %%MediciMedici

nene7373 51%51% 55 7%7%

SurgerSurgeryy

3636 25%25% 55 14%14%

ERER 3535 24%24% 55 14%14%OncoloOncolo

gygy1818 17%17% 66 25%25%

ICUICU 2424 13%13% 11 6%6%

All PatientsAll Patients PE+PE+

CTCT 105105 73%73% 1212 11%11%V/QV/Q 5353 37%37% 33 6%6%

BothBoth 1515 10%10% 33 20%20%

Hosp

ital

Service

Typ

e o

f PE

S

can

Pre-Test Probability of Pre-Test Probability of PEPE

## %% ## %%TotalTotal 144144 100%100% 1515 10%10%HighHigh 44 3%3% 00 0%0%

IntInt 6868 47%47% 1111 16%16%LowLow 7272 50%50% 44 5%5%

All PatientsAll Patients PE+PE+

HighHigh 1616 11%11% 33 19%19%IntInt 7575 52%52% 88 11%11%

LowLow 5353 37%37% 44 8%8%

Wells

Crite

riaP

IOP

ED

CT vs. V/Q ScanCT vs. V/Q Scan

## %% ## %%TotalTotal 105105 100%100% 5454 100%100%PE+PE+ 1212 11%11% 33 6%6%PE-PE- 8282 78%78% 4444 81%81%

Non-DiagnosticNon-Diagnostic 1111 10%10% 77 13%13%

CTCT V/QV/Q

Alt Dx, not on Alt Dx, not on CXRCXR

4444 42%42% 00 0%0%Changed Changed

Management*Management*8888 87%87% 3131 72%72%

Changed Changed Treatment*Treatment*

3535 35%35% 1111 26%26%

p-p-valuevalue

----------

0.090.09

0.230.23

0.560.56

<0.0<0.00101

0.0150.015

0.1160.116*Adjustment made for patients receiving both V/Q and CT scans to account for the test being surveyed by a particular physician. 15 patients received both CT and VQ scans. 11 of 15 surveys concerned CT scan change in management or treatment; 4 of 15 concerned the VQ scan.

More Data on V/Q ScansMore Data on V/Q Scans

25 of 54 (46%) patients undergoing V/Q 25 of 54 (46%) patients undergoing V/Q scan had no contraindication to CT scan.scan had no contraindication to CT scan.

The cost of a PE work-up was 23% greater The cost of a PE work-up was 23% greater for patients receiving a V/Q scan compared for patients receiving a V/Q scan compared to patients receiving a CT scan. to patients receiving a CT scan. The difference was not statistically significant.The difference was not statistically significant.

D-Dimer Use in Low Pre-D-Dimer Use in Low Pre-Test Probability PatientsTest Probability Patients

## %% ## %%Total Low ProbTotal Low Prob 7272 50%50% 5353 37%37%

Received D-DimerReceived D-Dimer 2929 40%40% 1919 36%36%Negative D-DimerNegative D-Dimer 55 18%18% 33 16%16%

Projected Savings* Projected Savings* per $1 spent on D-per $1 spent on D-

Dimer AssayDimer Assay

$6$6 $5$5

Wells Wells CriteriaCriteria

PIOPEDPIOPED

*Projected dollars saved if all low pre-test probability patients received a D-Dimer test and no further PE diagnostic testing was performed if the D-Dimer test was negative. Dollar values calculated based on the reported cost of each diagnostic test for an uninsured patient as reported by the University of Pennsylvania billing department in 4/2005.

Study LimitationsStudy Limitations Single CenterSingle Center Study did not include outpatientsStudy did not include outpatients Response bias – survey responders included Response bias – survey responders included

interns, residents, attending physicians, and interns, residents, attending physicians, and nurse practitioners.nurse practitioners.

Selection bias – Only included patients from Selection bias – Only included patients from inpatient and ED services during the work week.inpatient and ED services during the work week. Did not survey physicians overnight and on the Did not survey physicians overnight and on the

weekends.weekends. 2 reasons why study designed this way2 reasons why study designed this way

V/Q scanning only offered routinely during work weekV/Q scanning only offered routinely during work week Many scans requested overnight or on weekends have not Many scans requested overnight or on weekends have not

been discussed with an attending physicianbeen discussed with an attending physician

DiscussionDiscussion

This is the first known prospective This is the first known prospective observational study of physician observational study of physician practice patterns in PE diagnosis.practice patterns in PE diagnosis.

Two questions we sought to address Two questions we sought to address with this study:with this study: Is CT subjectively and/or objectively Is CT subjectively and/or objectively

superior to V/Q scan in suspected PE?superior to V/Q scan in suspected PE? Can the cost of PE work-up be reduced Can the cost of PE work-up be reduced

without compromising patient safety?without compromising patient safety?

CT > V/QCT > V/Q 3 recent systematic reviews* point out that 3 recent systematic reviews* point out that

withholding anticoagulation after a single negative CT withholding anticoagulation after a single negative CT scan is as safe as pulmonary angiography.scan is as safe as pulmonary angiography.

Although the non-diagnostic rate of V/Q scans was Although the non-diagnostic rate of V/Q scans was only 13% in this study, most literature reports 40%-only 13% in this study, most literature reports 40%-80% non-diagnostic rates for V/Q scans.80% non-diagnostic rates for V/Q scans.

According to PIOPED “Clinical Assessment combined According to PIOPED “Clinical Assessment combined with the V/Q scan established the diagnosis or with the V/Q scan established the diagnosis or exclusion of pulmonary embolism only for a minority of exclusion of pulmonary embolism only for a minority of patients – those with clear and concordant clinical and patients – those with clear and concordant clinical and V/Q scan findings” V/Q scan findings” (JAMA. 1990; 263: 2753-2759.)(JAMA. 1990; 263: 2753-2759.)

* Schoepf et. al. Circulation. 2004;109:2160-2167. Stevens et. al. Annals Int Med. 2004;140:985-991. Quiroz et al. JAMA. 2005;293:2012-2017.

CT > V/QCT > V/Q

Relative to CT, the V/Q scan was inferior Relative to CT, the V/Q scan was inferior in PE diagnosis. in PE diagnosis.

CT significantly superior to V/Q with CT significantly superior to V/Q with respect to respect to incidence changes in patient management incidence changes in patient management identifying alternate diagnosis not apparent identifying alternate diagnosis not apparent

on CXR. on CXR. Non-significant differences includedNon-significant differences included

incidence of PE diagnosis incidence of PE diagnosis cost of diagnostic work upcost of diagnostic work up

CT > V/QCT > V/Q

Conclusion: V/Q scanning is inferior to CT Conclusion: V/Q scanning is inferior to CT in the diagnosis of suspected PE and in the diagnosis of suspected PE and should be a second line test utilized in the should be a second line test utilized in the context of a contraindication to CT.context of a contraindication to CT.

D-DimerD-Dimer Multiple clinical trials,* suggest that Multiple clinical trials,* suggest that

withholding anticoagulation in patients with a withholding anticoagulation in patients with a negative D-Dimer and low pre-test probability negative D-Dimer and low pre-test probability is as safe as after a negative pulmonary is as safe as after a negative pulmonary angiogram.angiogram.

The 2003 British Thoracic Society guidelines The 2003 British Thoracic Society guidelines for PE diagnosis state that a patient with a for PE diagnosis state that a patient with a normal D-Dimer and a low pre-test probability normal D-Dimer and a low pre-test probability do not require further diagnostic imaging.do not require further diagnostic imaging. ATS guidelines have not been updated since 1999ATS guidelines have not been updated since 1999

* Wells et. al. Thromb Haemost 2000; 83:416-420 -- Wells et. al., Ann Int Med 2001; 135:98-107 -- Leclerq et. al. Thromb Haemost 2003; 89:97-103 – Perrier et. al. NEJM 2005;352(17):1760-8 -- Maricke et. al. Arch Int Med. 2002;162:1631-1635 – Musset et. al. Lancet. 2002;360:1914–1920 – Perrier et. al. Am J Med. 2004;116:291–299. – Kruip et. al. Arch Intern Med. 2002;162:1631–1635.

D-Dimer Reduces CostD-Dimer Reduces Cost

Conclusion: Greater reliance on D-Dimer Conclusion: Greater reliance on D-Dimer testing in low pre-test probability patients testing in low pre-test probability patients could result in substantial cost reduction in could result in substantial cost reduction in inpatients and ED patients suspected of PE.inpatients and ED patients suspected of PE. By extrapolation, if all low pre-test By extrapolation, if all low pre-test

probability patients received D-Dimers and probability patients received D-Dimers and those with negative D-Dimers were not those with negative D-Dimers were not imaged further, 1 year cost savings would imaged further, 1 year cost savings would total:total:

$500,000$500,000

ConclusionsConclusions

CT is superior to V/Q scanning for CT is superior to V/Q scanning for PE diagnosis in the absence of a PE diagnosis in the absence of a clear contraindication.clear contraindication.

Wider use of D-Dimer testing could Wider use of D-Dimer testing could substantially reduce the cost of PE substantially reduce the cost of PE exclusion.exclusion.

Co-Investigators Co-Investigators Abass Alavi, MD – Chief Department of Abass Alavi, MD – Chief Department of

Nuclear Medicine, University of Nuclear Medicine, University of PennsylvaniaPennsylvania

Warren Gefter, MD – Chief of Chest Warren Gefter, MD – Chief of Chest Radiology, University of PennsylvaniaRadiology, University of Pennsylvania

Harold Litt, MD – Chief of Cardiovascular Harold Litt, MD – Chief of Cardiovascular Imaging, University of PennsylvaniaImaging, University of Pennsylvania

Sandy Schwartz, MD – Professor of Sandy Schwartz, MD – Professor of Medicine, University of PennsylvaniaMedicine, University of Pennsylvania

Dan Sedehi, James Horowitz, Deepika Dan Sedehi, James Horowitz, Deepika Nemani, Sattar Gojrati – Highly Nemani, Sattar Gojrati – Highly dependable Penn Med Studentsdependable Penn Med Students

Final Thank YouFinal Thank You

Michael Adams, MD Residency Michael Adams, MD Residency Program Director; and Joseph Program Director; and Joseph Timpone, MD Director of Clinical Timpone, MD Director of Clinical Research – Georgetown University Research – Georgetown University Hospital, Department of Internal Hospital, Department of Internal MedicineMedicine

A big thanks to my chief residents, A big thanks to my chief residents, Tristan Huie and Jessica Gordon, for Tristan Huie and Jessica Gordon, for getting coverage for me today.getting coverage for me today.