ALDOSTERONE - plasma

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Specimen: 10 mL blood in chilled EDTA tube - plasma separated and frozen immediately. Cessation of diuretics or antihypertensive drugs at least two weeks prior to testing is preferred.

Method: Immunoassay. Peripheral venous (plasma) renin is usually assayed in conjunction with aldosterone; the aldosterone/renin ratio is calculated.

Reference Interval: Dependent on sodium intake, posture, drugs incl ACE inhibitors and diuretics.

Application: Investigation of hypertension when primary hyperaldosteronism (Conn’s syndrome) is suspected; this is commonly but not invariably associated with hypokalaemia. Documentation of hyperaldosteronism in the investigation of suspected renovascular hypertension.

Interpretation: The plasma aldosterone/renin ratio is of greater diagnostic value than either test alone. A high aldosterone/renin ratio suggests a mineralocorticoid abnormality; elevation of both aldosterone and renin to a similar extent suggests a renal abnormality. The result should be interpreted in consultation with the pathologist.

Reference: Lins P-E and Adamson U. Acta Endocrinologica 1986; 113: 564-569.

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