Pathology tests database

Sample and container requirements

EDTA Plasma (preferred) Serum

Minimum volume required

250 µL serum/plasma

Special requirements

When sent from other hospitals serum/plasma should be sent frozen but if it arrives thawed it may still be able to be processed depending on the timeframe for delivery.

Patient preparation

Ideally the laboratory should be provided with a full drug history and the patient's sodium and potassium status. Patients should preferably be off diuretic therapy and volume replete. Patients should be on a normal diet; on a low sodium diet the aldosterone could be 2-5 times that of normal. The sample does not need to be taken whilst the patient is fasting. Advice with regard to drug therapy should be sought from the relevant Endocrinologist. The measurement of aldosterone is best carried out at 8 am following at least 4 hours recumbence. This is because the change in blood pressure upon standing causes release of renin and therefore an increase in aldosterone. In practice most samples for aldosterone are taken randomly.

Sample viability

Turnaround time

10 working days

Reference range

Recumbant: <375 pmol/L (This relies on the patient lying down for at least 4 hours) Standing: <750 pmol/L For paediatric ranges, see: http://hyper.ahajournals.org/content/56/3/391.full 95th Percentile: 491 pmol/L 5th Percentile: 69 pmol/L

Clinical guidance

Please refer to LabTestsOnlineUK to learn more about aldosterone. https://labtestsonline.org.uk/tests/aldosterone-and-renin

Notes

Fludrocortisone does not cross-react in the assay. Aldosterone levels fall to very low levels with severe illness, so testing should not be done at times when a person is very ill. Stress and strenuous exercise can temporarily increase aldosterone results. The general investigation of the aldosterone:renin axis sometimes involves the use of posture studies. To convert from conventional units to SI units, multiply SA (ng/dL) × 27.743: pmol/L.