From the Guidelines
The Aldosterone-to-Renin Ratio (ARR) is 8.3, which is calculated by dividing the aldosterone level (13.45 ng/dL) by the renin activity (1.62 ng/ml/hr). This value falls within the normal range, as an ARR less than 20-30 (depending on the laboratory reference) is typically considered normal 1. The ARR is an important screening tool for primary aldosteronism, with elevated values suggesting possible hyperaldosteronism. In this case, the result does not suggest primary aldosteronism, as the ratio is below the cutoff value of 30 when plasma aldosterone concentration is reported in nanograms per deciliter (ng/dL) and plasma renin activity in nanograms per milliliter per hour (ng/mL/h) 1. Some key points to consider when interpreting ARR results include:
- The presence of very low renin levels can influence the ARR, and a plasma aldosterone concentration of at least 10 ng/dL is recommended to interpret the test as positive 1
- Patients should have unrestricted salt intake, serum potassium in the normal range, and mineralocorticoid receptor antagonists withdrawn for at least 4 weeks before testing 1
- The ARR has a high negative predictive value for screening of primary aldosteronism, but a high ratio has a low specificity for primary aldosteronism 1
- Factors that might affect aldosterone or renin levels, such as medications (particularly antihypertensives), posture during blood collection, time of day, and dietary sodium intake, should be considered when interpreting ARR results 1
From the Research
Calculation of Aldosterone-Renin Ratio (ARR)
To calculate the ARR, we need to divide the aldosterone level by the renin activity.
- Aldosterone level: 13.45 ng/dL
- Renin activity: 1.62 ng/ml/hr The ARR can be calculated as follows: ARR = Aldosterone level / Renin activity = 13.45 ng/dL / 1.62 ng/ml/hr = 8.30 ng/dL per ng/ml/hr 2
Interpretation of ARR
The calculated ARR value of 8.30 can be used to detect primary aldosteronism, as recommended by current guidelines 3, 2.
- A high ARR value may indicate primary aldosteronism, but confirmatory tests are often required to exclude false-positive results 3, 4, 5, 6.
- The ARR conveys key quantitative information that can simplify the diagnostic workup and ultimately result in better control of blood pressure 3.
Limitations
It is essential to note that the ARR should be interpreted in the context of other clinical and laboratory findings, as the ratio can be influenced by various factors, including the units of measurement used for aldosterone and renin 2.