In a patient with PAD presenting with a new ulcer, should the next step be a CT angiogram or an ABI test?

From the Guidelines

In a patient with peripheral arterial disease (PAD) presenting with a new ulcer, the next step should be an ankle-brachial index (ABI) test rather than a CT angiogram. The ABI is a simple, non-invasive, and cost-effective first-line diagnostic tool that provides valuable information about the severity of arterial insufficiency, as recommended by the American Heart Association 1. It involves measuring the ratio of systolic blood pressure at the ankle to that in the arm, with values below 0.9 indicating PAD and values below 0.4 suggesting severe disease that may contribute to ulceration.

The ABI test helps establish the vascular etiology of the ulcer and quantifies the degree of perfusion impairment. According to the 2024 ACC/AHA/AACVPR/APMA/ABC/SCAI/SVM/SVN/SVS/SIR/VESS guideline for the management of lower extremity peripheral artery disease, noninvasive imaging with duplex ultrasound, CTA, or MRA may be considered to establish the diagnosis of PAD in patients with suspected PAD and inconclusive ABI and physiological testing 2. However, in patients with a confirmed diagnosis of PAD, CTA, MRA, or catheter angiography should not be performed solely for anatomic assessment unless revascularization is being considered 2.

While CT angiography provides detailed anatomical information about arterial occlusions and stenoses, it should be reserved for patients who have abnormal ABI results and are being considered for revascularization procedures. CT angiography also carries risks including radiation exposure, contrast-induced nephropathy, and allergic reactions. Starting with the ABI follows a stepwise approach to diagnosis, beginning with simpler, less invasive tests before proceeding to more complex imaging studies when necessary for treatment planning.

Some key points to consider when deciding between ABI and CT angiogram include:

• The patient's clinical presentation and symptoms
• The need for revascularization procedures
• The risks associated with CT angiography
• The availability and cost of the tests
• The patient's overall health status and comorbidities. Given the most recent and highest quality evidence, an ABI test is the most appropriate next step in the diagnosis and management of a patient with PAD presenting with a new ulcer 2.

From the Research

Next Steps in Diagnosing Peripheral Artery Disease

In a patient with a history of peripheral artery disease (PAD) presenting with a new ulcer of the left lower extremity, the next appropriate step would involve further diagnostic testing to assess the severity of the disease and guide treatment. The two options considered here are a CT angiogram of the lower extremity and an ankle-brachial index (ABI) test.

Diagnostic Options

• CT Angiogram: This is a non-invasive imaging test that uses X-rays to take pictures of the blood vessels in the lower extremities. It can help identify blockages in the arteries and guide further treatment, such as angioplasty or surgery 3.
• Ankle-Brachial Index (ABI) Test: The ABI test is a simple, non-invasive test that compares the blood pressure in the ankles to the blood pressure in the arms. It can help diagnose PAD and assess its severity. However, studies have shown that ABI has a moderate predictive value in diagnosing lower extremity arterial disease, with a sensitivity of 72.3% and a specificity of 69.3% when using duplex ultrasonography as a reference standard 3.

Considerations for Choosing the Next Step

• Accuracy and Sensitivity: The ABI test has been shown to have variable accuracy for identifying significant stenosis, with sensitivity ranging from 15% to 79% in different studies 4.
• Patient Characteristics: The accuracy of the ABI test can be affected by patient characteristics, such as age and the presence of diabetes. In elderly individuals and patients with diabetes, the sensitivity of the ABI test may be lower 4.
• Clinical Presentation: The patient's clinical presentation, including the presence of a new ulcer, should be taken into account when choosing the next step. A CT angiogram may be more appropriate if there is a high suspicion of significant arterial disease or if the patient has a history of severe PAD 5.

Recommendations

Based on the available evidence, the next appropriate step in diagnosing PAD in a patient with a new ulcer of the left lower extremity would be to perform an ABI test, followed by further imaging studies such as a CT angiogram if the results are abnormal or if there is a high suspicion of significant arterial disease 3, 6, 7, 4, 5. However, the choice of test should be individualized based on the patient's clinical presentation and medical history.