Abi Calculation

Ankle-Brachial Index (ABI) Calculator

Brachial Systolic Pressure (Arms)

Right Ankle

Left Ankle

Results

Right ABI:

Left ABI:

*Interpretation is based on standard clinical guidelines for Peripheral Artery Disease (PAD).

function calculateABI() { var rArm = parseFloat(document.getElementById('rightArm').value); var lArm = parseFloat(document.getElementById('leftArm').value); var rDP = parseFloat(document.getElementById('rightDP').value); var rPT = parseFloat(document.getElementById('rightPT').value); var lDP = parseFloat(document.getElementById('leftDP').value); var lPT = parseFloat(document.getElementById('leftPT').value); if (isNaN(rArm) || isNaN(lArm) || isNaN(rDP) || isNaN(rPT) || isNaN(lDP) || isNaN(lPT)) { alert("Please enter all required systolic blood pressure values."); return; } // Highest arm pressure is the denominator for both calculations var highestArm = Math.max(rArm, lArm); // Right ABI calculation (Highest ankle pressure / Highest arm pressure) var highestAnkleRight = Math.max(rDP, rPT); var abiRight = highestAnkleRight / highestArm; // Left ABI calculation var highestAnkleLeft = Math.max(lDP, lPT); var abiLeft = highestAnkleLeft / highestArm; document.getElementById('resRight').innerText = abiRight.toFixed(2); document.getElementById('resLeft').innerText = abiLeft.toFixed(2); document.getElementById('interpRight').innerText = getInterpretation(abiRight); document.getElementById('interpLeft').innerText = getInterpretation(abiLeft); document.getElementById('abiResult').style.display = 'block'; } function getInterpretation(val) { if (val > 1.40) return "Interpretation: Non-compressible (Vessel Calcification)"; if (val >= 1.00) return "Interpretation: Normal"; if (val >= 0.91) return "Interpretation: Borderline"; if (val >= 0.41) return "Interpretation: Mild to Moderate PAD"; return "Interpretation: Severe PAD"; }

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Understanding the Ankle-Brachial Index (ABI)

The Ankle-Brachial Index (ABI) is a simple, non-invasive vascular test used to check for peripheral artery disease (PAD). PAD occurs when the arteries in your legs or arms become narrowed or blocked, typically due to plaque buildup (atherosclerosis), which reduces blood flow to your limbs.

How the ABI is Calculated

The calculation is a ratio derived from systolic blood pressure measurements. Specifically, it is the ratio of the highest blood pressure recorded at the ankle to the highest blood pressure recorded in the arms. To perform a thorough clinical ABI:

• Systolic pressure is measured in both the right and left brachial arteries (arms).
• Systolic pressure is measured at the Dorsalis Pedis (DP) and Posterior Tibial (PT) arteries in both ankles.
• The denominator for both legs is the highest of the two arm pressures.
• The numerator for each leg is the highest pressure found at that specific ankle.

Clinical Interpretation Table

ABI Range	Clinical Significance
> 1.40	Non-compressible arteries (common in diabetes or renal disease)
1.00 – 1.40	Normal blood flow
0.91 – 0.99	Borderline (Possible early PAD)
0.41 – 0.90	Mild to Moderate Peripheral Artery Disease
0.00 – 0.40	Severe Peripheral Artery Disease

Example ABI Calculation

Imagine a patient with the following systolic readings:

• Right Arm: 130 mmHg | Left Arm: 126 mmHg (Highest Arm = 130)
• Right Ankle: DP 110 mmHg, PT 115 mmHg (Highest Ankle = 115)

Calculation: 115 / 130 = 0.88

This result (0.88) would indicate mild to moderate peripheral artery disease in the right leg.

Why is ABI Important?

Low ABI scores are not only diagnostic for leg artery blockages but are also strong predictors of cardiovascular risk. Patients with a low ABI are at a higher risk for myocardial infarction (heart attack) and stroke because atherosclerosis is often a systemic condition affecting multiple vascular beds.

Note: This calculator is for educational purposes only and should not replace professional medical diagnosis. ABI measurements are typically performed by healthcare professionals using specialized Doppler ultrasound equipment.