Screening tool for Primary Aldosteronism (Conn's Syndrome)
ng/dL
pmol/L
Plasma Renin Activity (PRA)
Direct Renin Concentration (DRC)
What is the Aldosterone Renin Ratio (ARR)?
The Aldosterone-Renin Ratio is the primary screening test for Primary Aldosteronism (PA), a condition where the adrenal glands produce too much aldosterone. Excess aldosterone leads to high blood pressure (hypertension) and often low potassium levels (hypokalemia).
How to Interpret Results
Interpretation of the ARR varies depending on the laboratory and the units used. Generally, for PAC in ng/dL and PRA in ng/mL/h:
ARR < 20: Primary Aldosteronism is unlikely.
ARR 20 – 30: Suggestive of Primary Aldosteronism; often considered a "gray zone" requiring further evaluation.
ARR > 30: High probability of Primary Aldosteronism, especially if PAC is > 15 ng/dL.
Example Calculation
If a patient has a Plasma Aldosterone Concentration (PAC) of 30 ng/dL and a Plasma Renin Activity (PRA) of 0.5 ng/mL/h:
Calculation: 30 / 0.5 = 60
In this case, an ARR of 60 is significantly elevated, suggesting the need for confirmatory testing like a saline suppression test or oral salt loading test.
Important Medical Disclaimer: This calculator is for educational purposes only and is not a diagnostic tool. Factors such as medications (ACE inhibitors, beta-blockers, diuretics), salt intake, time of day, and posture can significantly affect ARR results. Always consult with an endocrinologist for clinical interpretation.
Units Conversion Table
If your results are in different units, our calculator handles the conversion. Common conversions include:
Aldosterone: 1 ng/dL = 27.7 pmol/L
Direct Renin Concentration (DRC) is often used as an alternative to PRA. While conversion factors vary by assay, a DRC of 8-12 mU/L is roughly equivalent to a PRA of 1 ng/mL/h.
function calculateARR() {
var aldo = parseFloat(document.getElementById('aldosteroneValue').value);
var aldoUnit = document.getElementById('aldosteroneUnit').value;
var renin = parseFloat(document.getElementById('reninValue').value);
var reninType = document.getElementById('reninType').value;
var resultArea = document.getElementById('arrResultArea');
var resultDisplay = document.getElementById('arrResultDisplay');
var interpDisplay = document.getElementById('arrInterpretation');
if (isNaN(aldo) || isNaN(renin) || renin <= 0) {
alert("Please enter valid positive numbers. Renin cannot be zero or negative.");
return;
}
// Convert Aldosterone to ng/dL if it's in pmol/L for standard ratio logic
var aldoInNgDl = aldo;
if (aldoUnit === 'pmoll') {
aldoInNgDl = aldo / 27.74;
}
var ratio = 0;
var unitLabel = "";
if (reninType === 'pra') {
// Standard Ratio: PAC (ng/dL) / PRA (ng/mL/h)
ratio = aldoInNgDl / renin;
unitLabel = "ng/dL per ng/mL/h";
} else {
// DRC Ratio: PAC (ng/dL) / DRC (mU/L)
ratio = aldoInNgDl / renin;
unitLabel = "ng/dL per mU/L";
}
resultArea.style.display = 'block';
resultArea.style.backgroundColor = '#f0f7fb';
resultDisplay.innerHTML = "Calculated ARR: " + ratio.toFixed(2);
var interpretation = "Interpretation:";
if (reninType === 'pra') {
if (ratio > 30) {
interpretation += "The ratio is elevated (>30). If PAC is also >15 ng/dL, this strongly suggests Primary Aldosteronism.";
resultArea.style.borderLeft = "5px solid #cc0000";
} else if (ratio >= 20) {
interpretation += "The ratio is in the 'gray zone' (20-30). Clinical correlation and potential retesting or confirmatory tests are recommended.";
resultArea.style.borderLeft = "5px solid #ffcc00";
} else {
interpretation += "The ratio is within the normal screening range ( 3.7) { // Common threshold for ng/dL per mU/L
interpretation += "The ratio is potentially elevated for DRC units. Please compare with your laboratory's specific reference range for Direct Renin Concentration.";
resultArea.style.borderLeft = "5px solid #cc0000";
} else {
interpretation += "The ratio appears low for DRC units, but reference ranges vary significantly between different assay manufacturers.";
resultArea.style.borderLeft = "5px solid #28a745";
}
}
interpretation += "Note: Ensure PAC was >10-15 ng/dL for the ratio to be most clinically relevant.";
interpDisplay.innerHTML = interpretation;
resultArea.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}