The Ankle-Brachial Index as a Screening Method for

Atherosclerosis

John Michael Frullo, Sana Yaklur, Lara Pferdehirt, Kathryn Wallace,

Sam Vallagomesa, Veronica Gough, Stephen Phillips, Paul Greenfield

Atherosclerosis in Today’s World

The Atherosclerosis Issue

• Plaque buildup on walls of arteries

• Causes blockage

• Can lead to heart attack or stroke

Scope and Statistics

• 400,000+ die annually from coronary heart disease related to atherosclerosis

• 50% of men and 64% of women who die of heart disease are not diagnosed

• Atherosclerosis Coronary Heart Disease

• Often undetected

• Diagnosis is expensive and invasive

• Prevention is possible through early detection

• Currently no standard method

Problem Statement

Mission Statement

Identify individuals at risk

Choose a method to classify people into risk groups

Minimize cost to society

Key Results

• Screen an intermediate and high risk population for atherosclerosis

• Using the Ankle-Brachial Index

• Extend ≈800,000 lives in the first year

• Save $27.7 billion in the first year

Target Design Criteria

Design Criteria Desired Measure

Cost ≤ $30

Sensitivity 85%

Specificity 50%

Accessibility Suburban/Urban Clinic

Administration General Practitioner

Assumptions

• Numerical data related to CHD is also applicable for atherosclerosis• Costs from healthcarebluebook.com • Most hospitals equipped to:

otake blood pressureodraw bloodoconduct blood analysis

3 Screening Methods

Low Density Lipoprotein (LDL) Cholesterol Testing

High-Sensitivity C-Reactive Protein (hs-CRP)

Ankle-Brachial Index (ABI)

Low Density Lipoprotein (LDL) Cholesterol Testing

• LDL, risk of cardiovascular diseases

• Cost: $50• Sensitivity and

specificity: 88%

High-Sensitivity C-Reactive Protein

• CRP biomarker showing inflation

• Cost: $80• Sensitivity: 93%• Specificity: 65%

Ankle-Brachial Index

• Blood pressure measurements at arm and ankle

• Cost: $20• Sensitivity: 85%• Specificity: 45%• Simple

implementation

PUGH SCORING MATRIX Ankle-Brachial Index hs-CRP Cholesterol Testing

(LDL)

Evaluation Criteria Weight Raking Weighted

Score Ranking Weighted Score Ranking Weighted

Score

Cost 40% 5 2.00 2 0.80 3 1.20

Sensitivity 20% 2 0.40 4 0.80 3 0.60

Specificity 15% 3 0.45 4 0.60 5 0.75

Accessibility 15% 3 0.45 3 0.45 3 0.45

Administration 10% 4 0.40 3 0.30 4 0.40

Total Weighted Score

100% 3.70 2.95 3.40

Rank - 1 3 2

Chosen - IMPLEMENT NO NO

Ankle-Brachial Index

• Administration• Possible Results:

o ≥ 0.9: good cardiovascular healtho < 0.9: indication of arterial problems

Posterior Tibial Artery Blood Pressure

Brachial Artery Blood Pressure

Population• Selection Process:

o Ages when risk increaseso Risk factors derived from Framinghamo Targeting intermediate/high risk group

• Risk Factors:1. Family history of Coronary Heart Disease2. Obesity3. Physical Activity4. Smoking

Men: 45-65 yearsWomen: 55-65 years

U.S. Population

≥ 2 risk factors

Ankle-Brachial Index

HIGH RISK GROUPLOW RISK GROUP

≥ 0.9 < 0.9

LOW RISK GROUP HIGH RISK GROUP

• Maintain a healthy lifestyle (especially in the risk factor categories)

• Rescreen in two years

• Consult doctor for:• diagnosis

(angiography)• treatment

Cost-Benefit Analysis

• 11.1 million people screened• Add 2.6 years of life• Save $27.7 billion in the first year

Cost: $24.4 billion

Benefit: $52.1 billion

Benefit to Cost Ratio = 2.14 : 1

Limitations of Ankle-Brachial Index

• Disadvantageo Relatively low specificity value (45%)

Test Positive Test Negative

Actual Positive True Positive False Negative(Sensitivity)

Actual Negative False Positive(Specificity) True Negative

Advantages of Ankle-Brachial Index

• Cost: $20• Sensitivity: 85%• Accessibility

o Most Hospitals and Clinics• Administration

o Requires 2 hours of trainingoMost medical professionals

Conclusion

• Atherosclerosis & CHD ultimately fatal, but preventable

• Screening is the best solution• We recommend screening using the

Ankle-Brachial Indexo Intermediate and high risk population

• Save $27.7 billion, Benefit to Cost (2.14:1)

Reference Slide1. What is Atherosclerosis? (n.d.). National Heart, Lung and Blood Institute.

Retrieved from http://www.nhlbi.nih.gov/health/health-topics/topics/atherosclerosis/2. . What Is Coronary Heart Disease? (n.d.). National Heart, Lung, and Blood Institute.

Retrieved from http://www.nhlbi.nih.gov/health/health-topics/topics/cad/3. Castellon, X., & Bogdanova, V. (2013). Screening for subclinical atherosclerosis by

noninvasive methods in asymptomatic patients with risk factors. Clinical Interventions in Aging, 2013(8), 573 – 580.

4. Carotid Angiogram: How to prepare for your procedure . (n.d.). University of Washington Medical Center. Retrieved from

https://healthonline.washington.edu/document/health_online/pdf/Carotid_Angiogam_7_08.pdf5. What is Cholesterol? (2012, September 19). National Heart, Lung, and Blood

Institute. Retrieved from http://www.nhlbi.nih.gov/health/health-topics/topics/hbc/ 6. Miller, W. G., Myers, G. L., Sakurabayashi, I., Bachmann, L. M., Caudill, S. P.,

Dziekonski, A., … Remaley, A. T. (2010). Seven Direct Methods for Measuring HDL and LDL Cholesterol Compared with Ultracentrifugation Reference Measurement Procedures. Clinical Chemistry, 56(6), 977–986. doi:10.1373/clinchem.2009.142810

7. Low Density Lipoprotein Cholesterol (Direct). (2013).Healthcare Blue Book. Retrieved from http://healthcarebluebook.com/page_Results.aspx?id=1072&dataset=lab&g=Lo w-Density%

20Lipoprotein%20Cholesterol%20(Direct 8. Rifai, Nader, and Paul M. Ridker. “High-Sensitivity C-Reactive Protein: A Novel and

Promising Marker of Coronary Heart Disease.” Clinical Chemistry 47, no. 3 (March 1, 2001): 403–411. http://www.clinchem.org/content/47/3/403.

Reference Slide(2)9. High Sensitivity C-Reactive Protein Testing for Cardiovascular Disease. (2013, April

9). Blue Cross Blue Shield of Tennessee. Retrieved from http://www.bcbst.com/learn/treatment-options/crp.shtm 10. Diercks, D. B., Kirk, J. D., Naser, S., Turnipseed, S., & Amsterdam, E. A. (2011).

Value of high-sensitivity C-reactive protein in low risk chest pain observation unit patients. International Journal of Emergency Medicine, 4, 37. doi:10.1186/1865-1380-4-37. Retrieved from

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3141386/ 11. Ankle-brachial index. (2006).Harvard Medical School Family Health Guide.

Retrieved from http://www.health.harvard.edu/fhg/updates/ankle-brachial-index.shtml12. Crimmel, B.L. Co-pays and Coinsurance Percentages for Employer-Sponsored Health

Insurance in the Private Sector, by Firm Size Classification, 2002–2005. Statistical Brief #189. November 2007. Agency for Healthcare Research and Quality, Rockville, MD. 13. Thoshiaki Shinozaki, , T. H., & Eiji Yano. (1998). Ankle–Arm Index as an Indicator

of Atherosclerosis: Its Application as a Screening Method. Journal of Clinical Epidemiology, 51(12), 1263–1269. doi:http://dx.doi.org/10.1016/S08954356(98)00122-X

14. Coronary Heart Disease (10-year risk) Framingham Heart Study. (n.d.). RetrievedSeptember 17, 2013, from http://www.framinghamheartstudy.org/risk/coronary.html

15. Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). (2002, September). National Heart, Lung, and Blood Institute. Retrieved from

Reference Slide(3)16. Naghavi, M., Falk, E., Hecht, H. S., Jamieson, M. J., Kaul, S., Berman, D., … Shah,

P. K. (2006). From Vulnerable Plaque to Vulnerable Patient—Part III: Executive Summary of the Screening for Heart Attack Prevention and Education (SHAPE) Task Force Report.The American Journal of Cardiology, 98(2, Supplement 1), 2– 15.doi:10.1016/j.amjcard.2006.03.002

17. Lalkhen, A. G., & McCluskey, A. (2008). Clinical tests: sensitivity and specificity.Continuing Education in Anaesthesia, Critical Care & Pain, 8(6), 221

223. doi:10.1093/bjaceaccp/mkn041 18. Mohler III, E., Treat-Jacobson, D., Reilly, M., Cunningham, K., Miani, M., Criqui,

M., … Hirsch, A. (2004). Utility and barriers to performance of the ankle brachial index in primary care practice. Vascular Medicine, 9(243), 253 – 260. doi:10.1191/1358863x04vm559oa. Retrieved from http://vmj.sagepub.com/content/9/4/253.long.

Picture Reference

• http://www.foxnews.com/health/2013/05/30/high-doses-common-painkillers-increase-heart-attack-risks/ [Heart Clutch]

• http://familydoctor.org/content/familydoctor/en/diseases-conditions/atherosclerosis/_jcr_content/par/image.img.png [Athero]

• http://www.wakemed.org/images/heartcenter/H2H_Spring2011_anckle.jpg [ABI]• [Slide 2 - Hook] http

://lebanonfamilyhealth.org/wp-content/uploads/2013/01/lfhs_website_header_images.jpg

• [Slide 2 - Hook] http://www.thebestsuccesscoach.com/wp-content/uploads/2013/02/shutterstock_124099558-200x300.jpg

• [Pop. Infographic] http://www.thebestsuccesscoach.com/wp-content/uploads/2013/02/shutterstock_124099558-200x300.jpg

• http://www.scientificamerican.com/article.cfm?id=next-generation-blood-test • http://www.examiner.com/article/pacquiao-says-he-is-now-open-to-do-random-bl

ood-tests-with-14-day-cutoff-for-mayweather-fight

SCORING MATRIX

Ankle-Brachial

IndexCIMT

Coronary Calcium

Scorehs-CRP ECG LDL Test

Cost + 0 - + - +

Sensitivity 0 0 + + - 0

Specificity - 0 - 0 + +

Accessibility + 0 0 + 0 +

Administration + 0 - - - +

Sum of +, 0, -+: 30: 1-: 1

+: 00: 5-: 0

+: 10: 1 -: 3

+: 30: 1-: 1

+: 10: 1-: 3

+: 40: 1-: 0

Rank 2 4 5 2 5 1

Pass? YES NO NO YES NO YES

5 0-24

4 25-49

3 50-74

2 75-99

1 ≥ 100

5 96-100

4 91-95

3 86-90

2 81-85

1 76-80

5 80-100

4 60-79

3 40-59

2 20-39

1 0-19

5 At home

4 Suburban/Rural Clinic

3 Most Urban Hospitals

2 Specialized Hospitals

1 No available in the U.S.

5 Anybody (at home)

4 Technician/Nurse/Blood Tests: any lab

3 Family Practitioner/Blood Tests: labs with more diverse options

2 Cardiologist

1 Specialized Cardiologist

Table 1: Cost Scale (in USD) Table 2: Sensitivity Scale (%) Table 3: Specificity Scale (%)

Table 4: User-Defined Scale Accessibility Table 5: User-Defined Scale Administration

Cost Benefit Analysis

Population Numbers (people)

Test Positive Test Negative

Actual Positive TP: 800,000 FN: 140,000

Actual Negative FP: 5.6 mill TN: 4.56 mill

6.4 million

11.1 million

60.3 million

Flier

ABI

Angiography

Cost Benefit Analysis• Benefit = $52.1 billion– Lives saved * Life-years/person * Monetary

value/ Life-year– 800,000 people * 2.6 years/person * $25,000/yr

• Cost = $24.4 billion– Costs of: fliers + screening + angiography +

patient time + doctor time– $661 mill + $222 mill + $9.18 bill + $445 mill +

$13.9 bill• Benefit to Cost Ratio = 2.14 : 1