Clinical Review & Education

JAMA Diagnostic Test Interpretation

Coronary Artery Calcium Score Tamar S. Polonsky, MD, MSCI; Roger S. Blumenthal, MD; Philip Greenland, MD

A 58-year-old woman presents to a cardiologist’s office to discuss her cardiovascular disease (CVD) risk. She is asymptomatic and has never smoked. She has a history of hypothyroidism and swims 4 times a week for 30 minutes. Her brother experienced a myocardial infarction (MI) at age 59. Prior to his MI, her brother was a vegetarian and an avid runner without hypertension or dyslipidemia. His 10-year atherosclerotic cardiovascular disease (ASCVD) risk was 7% (calculated based on traditional risk factors). Her father was a smoker and had an MI at age 66. The patient’s blood pressure is less than 120/80 mm Hg without medication. Her body mass index is 21.3. Her estimated 10-year ASCVD risk is 2% based on traditional risk factors. However, her low-density lipoprotein cholesterol (LDL-C) level has increased. Her most recent lipid panel showed a total cholesterol level of 286 mg/dL, triglycerides of 75 mg/dL, HDL-C level of 106 mg/dL, and LDL-C of 165 mg/dL. Because of her family history and increasing LDL-C, she underwent a cardiac computed tomography (CT) scan to measure her coronary artery calcium (CAC) score. Her CAC score is 88 (normal value = 0 Agatston units) (Table). Table. Excerpt From the Patient’s Cardiac Computed Tomography Reporta

Left main Left anterior descending Circumflex

Agatston Score 0 69 0

Right coronary artery

19

Total

88

Answer D. The patient should continue aggressive lifestyle changes and consider statin therapy.

Test Characteristics CAC is estimated from noncontrast CT images obtained from a multidetector row scanner. Calcium appears white on the CT image (Figure) and the intensity of the calcium signal is assigned a value ranging from 1 to 4, with 4 being the densest. The area of each plaque is measuredandmultipliedbytheintenJAMA Patient Page page 858 sity index, yielding a number knownastheAgatstonunit.Theresultingnumbersaresummedforeach coronary artery plaque, producing a CAC score. Usually coronary arteriesdonothaveplaquesorcalciumandthenormalscoreis0.ACACscore of 300 or higher or 75th percentile or higher for age, sex, and ethnicity is considered high risk.1,2 The CAC score is strongly correlated with the overall atherosclerotic burden and has highly reproducible results.3 CAC measurement improves CVD risk classification over traditional risk factors substantially more than does inclusion of ankle-brachial index or high-sensitivity C-reactive protein in risk classification schemes.4,5 Limitations include that a CAC-guided treatment strategy has not beenstudiedinarandomizedtrialpoweredforclinicalevents.CACtestingmaybeassociatedwithincidentalfindings(eg,pulmonarynodules) in about 5% to 10% of adults.6 Medicare does not cover CAC testing to screen for subclinical CVD. Out-of-pocket cost—including imaging and jama.com

a Coronary findings impressions: mild coronary calcification; Agatston calcium score (88) represents the 92nd percentile for age, sex, and ethnicity.

HOW DO YOU INTERPRET THESE TEST RESULTS?

A. The patient’s CVD risk is not elevated because her CAC score is

Coronary artery calcium score.

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