Aldosterone

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.

Immunoassay.

Peripheral venous (plasma) renin is usually assayed in conjunction with aldosterone. The aldosterone/renin ratio is calculated.

Dependent on sodium intake, posture, drugs including ACE inhibitors and diuretics.

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.

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.