Aldosterone

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 including 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 mineralocorticoid excess (primary hyperaldosteronism).

Elevation of both aldosterone and renin to a similar extent suggests a renal abnormality (secondary hyperaldosteronism). The result should be interpreted in consultation with the pathologist.

Reference:

Veglio F et al. Minerva Med 2003; 94: 259-265.