I notice there may be a misunderstanding in your question. The ankle-brachial index (ABI) is not a medical licensing exam—it is a diagnostic test used to detect peripheral arterial disease (PAD).
What is the Ankle-Brachial Index?
The ABI is a simple, non-invasive vascular test that compares blood pressure measurements between the ankle and arm to diagnose lower extremity arterial disease 1.
How It Works
- A blood pressure cuff is placed on the upper arm and just above the ankle
- Doppler ultrasound measures systolic pressures in both locations
- The ABI is calculated by dividing the highest ankle systolic pressure by the highest brachial systolic pressure 2, 1
Diagnostic Thresholds
- Normal ABI: 0.90-1.40
- Abnormal (PAD present): ≤0.90 (75% sensitivity, 86% specificity for diagnosing PAD) 2
- Borderline: 0.90-1.00 (requires further testing)
- Non-compressible arteries: >1.40 (common in diabetes, chronic kidney disease, elderly—requires alternative testing like toe-brachial index) 2, 1
Clinical Indications
The ABI is recommended as the first-line diagnostic test after clinical examination for screening and diagnosing peripheral arterial disease (Class I recommendation) 2. It is particularly useful for:
- Patients with exertional leg pain (claudication)
- Assessing healing potential of foot wounds
- Cardiovascular risk stratification
- Follow-up after revascularization procedures 2
Important Limitations
The ABI has reduced sensitivity in patients with diabetes or end-stage chronic kidney disease due to medial arterial calcification, which makes vessels incompressible 2, 1. In these cases, alternative tests such as toe-brachial index (TBI <0.70 is abnormal), Doppler waveform analysis, or transcutaneous oxygen pressure should be used 1.
If you were asking about which medical licensing exams (USMLE, COMLEX, etc.) test knowledge of the ABI, this topic is covered in standard medical education as part of cardiovascular and vascular medicine curricula, but that's a different question entirely.