What is the role of aldosterone-to-renin ratio (ARR) in the diagnosis of hyperaldosteronism?

Updated: Oct 19, 2018
  • Author: George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London); Chief Editor: Robert P Hoffman, MD  more...
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Answer

The aldosterone-to-renin ratio (ARR)—that is, the ratio of plasma aldosterone (expressed in ng/dL) to plasma renin activity (PRA, expressed in ng/mL/h)—is the most sensitive means of differentiating primary from secondary causes of hyperaldosteronism. It can be obtained under random conditions of sodium intake.

The principle behind this test is that as aldosterone secretion rises, PRA (which measures the rate of production of angiotensin I from endogenous angiotensinogen) in ex vivo testing should fall because of sodium retention. This negative feedback response should occur when the aldosterone levels are supraphysiologic for that individual patient, and PRA may fall well before plasma aldosterone is clearly increased.

Values obtained in the upright position (ie, with the patient standing for 2 h) are more sensitive than supine test results. Patients should be encouraged not to restrict salt intake and hypokalemia should be corrected before testing because low potassium suppresses aldosterone secretion. Most authors recommend an ARR of 20-40, whereas an ARR of at least 35 has 100% sensitivity and 92.3% specificity in diagnosing PA. Some investigators require elevated aldosterone levels in addition to elevated ARR for a positive screening test for PA (usually aldosterone >15 ng/dL). Against a formal cut-off level for aldosterone are the findings of several studies, indicating that 36–48% of individuals with PA have plasma aldosterone levels between 9–16 ng/dL and approximately 20% of individuals with unilateral autonomous adrenal aldosterone production have levels less than 15 ng/dL. [3, 22, 24, 25]


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