Case Study

K.A. is a 63-year-old man who presents for a routine wellness examination. His blood pressure and cholesterol level are within normal limits, and he has no history of tobacco use or heart disease. K.A. mentions that a former colleague had a stroke from carotid artery stenosis and asks whether he might be at risk.

Case Study Questions

1. Based on information from the U.S. Preventive Services Task Force (USPSTF), which of the following is/are considered major risk factors for carotid artery stenosis?

• A. Male sex.

• B. Hypertension.

• C. Smoking.

• D. High cholesterol.

2. According to the USPSTF, which of the following statements about noninvasive screening for carotid artery stenosis is correct?

• A. There are no harms associated with screening methods that use noninvasive technology.

• B. A positive screening result is often confirmed with more accurate tests, which can cause serious adverse events.

• C. A negative screening result indicates that the patient has no health problems.

• D. Ultrasonography can induce a stroke.

• E. The stress of undergoing a screening test can induce a heart attack.

3. Which one of the following statements best reflects the USPSTF recommendation for screening for carotid artery stenosis?

• A. Asymptomatic men older than 60 years should be screened once for carotid artery stenosis.

• B. Women should be screened annually because they are at higher risk of carotid artery stenosis than men.

• C. Men should be screened for carotid artery stenosis every five years after 70 years of age.

• D. Screening for asymptomatic carotid artery stenosis in the general adult population is not recommended.

• E. The benefits of screening asymptomatic adults for carotid artery stenosis outweigh the potential harms of further testing and treatment.

Answers

1. The correct answers are A, B, C, and D. The major risk factors for carotid artery stenosis include older age, male sex, hypertension, smoking, hypercholesterolemia, and heart disease.

2. The correct answer is B. Tests to confirm carotid duplex ultrasonography have associated harms. If all positive test results were followed by digital subtraction angiography, about 1 percent of patients would experience a nonfatal stroke as a result of angiography. If positive test results were not followed by confirmatory angiography, but rather by magnetic resonance angiography or computed tomography angiography—tests with less than 100 percent accuracy—patients with false positives would have unnecessary carotid endarterectomy with consequent harms in the absence of proven benefit. False negatives are also a potential harm of screening tests. Quantifying false negatives is difficult because many studies on the accuracy of screening do not perform the gold standard test on negative results.

3. The correct answer is D. From population-based studies and the accuracy of carotid duplex ultrasonography, the estimated prevalence of 60 to 99 percent stenosis in persons older than 65 years is about 1 percent. Research has not found a single risk factor or clinically useful risk stratification tool that can reliably and accurately distinguish people who have clinically important carotid artery stenosis from those who do not.

In a setting of excellent surgical care and low complication rates, screening may benefit patients who have a high risk of stroke. It is not clear, however, how to identify persons whose risk of stroke is high enough to justify screening, but who do not have a high risk of surgical complications. The USPSTF concludes that for persons with asymptomatic carotid artery stenosis, there is moderate certainty that the benefits of screening do not outweigh the harms.