Please refer to the Trust’s phlebotomy procedure for sample collection precautions.

This investigation should only be undertaken if the patient:

Gross potassium depletion inhibits aldosterone production and may lead to a normal value being found in Conn’s syndrome. Potassium supplements should therefore be given until the serum potassium is within the reference range (3.5-5.0 mmol/l) or has reached a maximum value. Supplements should then be discontinue the day before the samples are taken with the patients continuing to receive an adequate sodium and potassium intake (Sodium: 100-300 mmol/day, Potassium: 50-100 mmol/day).

All drugs should be discontinued for 2 weeks before samples are collected. If the patient is being treated with aldosterone antagonists (e.g. spironolactone) or oestrogens, the therapy must be discontinued for at least 6 weeks before the aldosterone-renin system is assessed. If the patient's hypertension is such that all drug therapy cannot be withdrawn safely, the a -blocker prazosin has little effect on the aldosterone-renin system. Calcium channel blockers and ACE inhibitors must be avoided.

It is imperative that the Clinical Biochemistry Department is informed before these tests are undertaken so that arrangements can be for specimen collection and handling.
The urine collections for electrolytes and then for aldosterone can be made at home on the 2 days preceding an overnight admission to hospital for collection of the blood samples. The patient may then be discharged (on hypotensive therapy if necessary).

The blood should have been collected into PLASTIC lithium heparin tubes and transported to the laboratory immediately. Mix and centrifuge immediately, and transfer plasma to a second PLASTIC tube. Store plasma for Renin at –20°C and Aldosterone at +4°C. Samples should be labelled with date/time and sent to referral laboratory as soon as possible (Renin sent frozen).

Primary hyperaldosteronism by an elevated aldosterone value at 08.00hrs, together with a suppressed renin which shows little or no increase after 30 minutes of mobility. An elevated aldosterone level at 08.00hrs decreasing by 50% or more at 12.00hrs is suggestive of an adenoma or glucocorticoid-suppressible hyperaldosteronism.