Investigation of disorders of aldosterone production. Both initial diagnosis and differentiation between the conditions listed below require concomitant plasma Renin activity (PRA) measurements.
- Primary hyperaldosteronism
- Conn′s syndrome and related conditions.
- Secondary hyperaldosteronism
- The only form of secondary hyperaldosteronism in which the assay of aldosterone is of value is Bartter′s syndrome.
Aldosterone assays are not helpful in patients with secondary hyperaldosteronism associated with nephrotic syndrome, cirrhosis etc or with renal hypertension, although the measurement of PRA may assist management.
- Secondary hypoaldosteronism
- Hyporeninaemic hypoaldosteronism.
- Primary hypoaldosteronism
- Isolated deficiency of aldosterone synthesis.
- Aldosterone insensitivity syndrome.
Up to 630pmol/L
Spironolactone, calcium channel blockers, ACE inhibitors and Angiotensin receptor blockers should be stopped 6 weeks before taking sample, if clinically possible. Additionally any hypertensive drug therapy should be stated by the requester at time of sampling. If the patient’s hypertension is such that all drug therapy cannot be withdrawn safely, the B-blocker, prazosin, has little effect on the aldosterone-renin system. B-blockers and diuretics have predictable effects but calcium channel blockers and ACE inhibitors must be avoided. Interpretation is particularly difficult when the patient is on a mixed-drug regime. The patient must be receiving an adequate intake of sodium (100-150 mmol/day) and potassium (50-100 mmol/day). In order to mimise false positive results patients ideally should observe strict overnight recumbency. After waking, the patient must remain lying down and must not alter posture in any way until after the initial blood sample has been taken.
Samples for the assay of aldosterone only may be made on Plasma or Serum (SST). If renin activity measurement is required, the sample must be plasma.
South Manchester Hospital