Clinical use
Investigation of disorders of aldosterone production, most commonly suspected primary hyperaldosteronism (also referred to as Conn’s syndrome) which is usually caused the presence of an adrenal adenoma, adrenal hyperplasia or less commonly an adrenal carcinoma.
Both aldosterone and renin are measured together as part of initial and subsequent investigations (both aldosterone and renin can be measured on the same specimen).
Background
Aldosterone in conjunction with renin and angiotensin plays an important role in regulating blood volume and systemic vascular resistance, which together influence cardiac output and arterial pressure. Hyperaldosteronism overrides this regulatory control resulting in retention of sodium with subsequent volume expansion and hypertension, leading to an increased risk of atrial fibrillation, coronary artery disease, heart failure and stroke.
Measurement of aldosterone and renin and calculation of the aldosterone:renin ratio (ARR) is the first line investigation for suspected hyperaldosteronism. In cases in which the ARR is raised then further confirmatory testing (e.g. saline infusion testing, adrenal imaging) is required.
Reference ranges
Up to 630pmol/L
Patient preparation
The Endocrine Society guidance recommends that prior to taking specimen for aldosterone/renin:
- If present, attempt to correct hypokalaemia (potassium ideally within the reference range)
- Encourage liberal salt (sodium) intake in the days before testing
- In the 4 weeks before testing, withdraw medications that can significantly affect ARR (e.g. amiloride, potassium wasting diuretics, spironolactone)
- In the 2 weeks before testing, withdraw beta-blockers and alpha-2-agonists
Withdrawing medications & beta-blockers
Only do if safe to do so; alternative non-interfering agents may be considered instead.
Specimen requirements
EDTA (purple top) tube
Special requirements
This should be transported to the laboratory within 30 minutes at room temperature. Specimens should not be transported on ice, as this will cause inaccurate renin measurements.
Minimum volume
3ml
Limitations/Restrictions
This should be transported to the laboratory within 30 minutes at room temperature. Specimens should NOT be transported on ice, as this will cause inaccurate renin measurements.
Turnaround time
4 weeks
Analysing laboratory
Department of Clinical Biochemistry, Wythenshawe Hospital, Southmoor Road, Wythenshawe, Manchester, M23 9LT