Ankle-Brachial Index (ABI)

The Ankle-Brachial Index (ABI) is a quick, non-invasive method used to evaluate vascular status and detect peripheral arterial disease (PAD). First described by Winsor in 1950, the ABI provides a simple way to compare blood pressure in the legs and arms, making it a valuable tool for the early diagnosis of arterial obstruction【1】【2】【3】.

Summary

The ABI is a fast, painless test for assessing vascular health and identifying PAD. By measuring systolic blood pressure in both the arms and ankles, it can reveal arterial blockages and estimate the risk of severe complications.

Since 1950, the ABI has been widely used in patients with symptoms such as intermittent claudication, slow-healing wounds, or cold and discolored legs. While less reliable in certain groups, such as those with diabetes, it remains an important tool for early detection and clinical decision-making.

Indications

ABI is indicated in patients with suspected PAD, including those presenting with:

• Intermittent claudication: Cramping pain in the legs during walking【4】

• Slow-healing wounds: Particularly in the lower limbs【5】

• Temperature or color changes: Cold or discolored feet and legs【6】

High-risk groups should also be screened, including patients with a history of smoking, diabetes, hypertension, or prior stroke【4】【5】.

Contraindications

ABI should not be performed in:

• Patients with confirmed or suspected deep vein thrombosis (DVT), due to risk of embolization

• Patients experiencing severe leg pain preventing accurate measurement【5】

Procedure

Required equipment:

• Handheld Doppler ultrasound

• Blood pressure cuff【7】

Step-by-step method:

1. Preparation: Patient rests supine for 10–20 minutes. Avoid nicotine at least 2 hours before testing.

2. Measurement: Place the cuff on the arm and record brachial systolic pressure using Doppler. Repeat at the ankle, measuring both dorsalis pedis and posterior tibial arteries【8】.

3. Calculation: Divide the highest ankle systolic pressure by the highest brachial systolic pressure. Perform on both legs【8】.

Interpretation of Results

ABI Value	Interpretation	Recommendation
< 0.5	Severe arterial disease	Refer to vascular surgery【8】
0.5–0.8	Moderate arterial disease	Refer to vascular surgery【8】
0.8–0.9	Mild arterial disease	Manage risk factors【8】
0.9–1.0	Acceptable range	No action required【8】
1.0–1.4	Normal range	No action required【8】
> 1.4	Arterial calcification	Specialist referral【8】

Advantages and Limitations

Advantages

• Quick, simple, and inexpensive

• Non-invasive and painless

• High test–retest reliability【9】

Limitations

• Less sensitive in patients with diabetes or arterial calcification【10】

• Limited ability to assess microvascular perfusion【11】

Conclusion

The Ankle-Brachial Index (ABI) is a valuable diagnostic tool for assessing PAD. Despite some limitations, it provides critical insights into a patient’s vascular health and supports early diagnosis and treatment planning.

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Referanser

1. Winsor, T. "Influence of arterial disease on the systolic blood pressure gradients of the extremity." Am J Med Sci. 1950 Aug;220(2):117-26.

2. McClary, K.N., Massey, P. "Ankle Brachial Index." StatPearls, 2022.

3. Mayo Clinic. "Ankle Brachial Index." Tilgjengelig fra: https://www.mayoclinic.org/tests-procedures/ankle-brachial-index/about/pac-20392934

4. Ankle Brachial Index: Quick Reference Guide for Clinicians. Journal of Wound, Ostomy and Continence Nursing: March/April 2012 - Volume 39 - Issue 2S - p S21-S29.

5. Harvard Health Publishing. "Ankle-brachial index." Tilgjengelig fra: https://www.health.harvard.edu/newsletter_article/ankle-brachial-index

6. Mayo Clinic. "Doppler ultrasound: What is it used for?" Tilgjengelig fra: https://www.mayoclinic.org/doppler-ultrasound/expert-answers/faq-20058452

7. Stanford Medicine. "Introduction to Measuring the Ankle Brachial Index." Tilgjengelig fra: https://stanfordmedicine25.stanford.edu/the25/ankle-brachial-index.html

8. Crawford, F., et al. "Ankle Brachial Index for the Diagnosis of Lower Limb Peripheral Arterial Disease." Cochrane Database of Systematic Reviews, 2016.

9. Casey, S., et al. "The reliability of the ankle-brachial index: a systematic review." J Foot Ankle Res. 2019 Aug 2;12:39.

10. Abouhamda, A., Alturkstani, M., Jan, Y. "Lower sensitivity of ankle-brachial index measurements among people suffering with diabetes-associated vascular disorders." SAGE Open Med. 2019 Mar 1;7:2050312119835038.

11. Davidson, B.P., et al. "Limb Perfusion During Exercise Assessed by Contrast Ultrasound Varies According to Symptom Severity in Patients with Peripheral Artery Disease." J Am Soc Echocardiogr. 2019 Sep;32(9):1086-1094.e3.