Pathology Handbook

Aldosterone and Renin

Clinical Indications

Investigation of primary hyperaldosteronism.

Request Form

Request on ICE

Availability

Analysed by referral laboratory if specific criteria met

Specific Criteria

Requested by Consultant Renal Physicians or if agreed with Consultant Biochemist. Investigation will normally only be undertaken if patient has persistent hypokalaemia (< 3.5 mmol/l) and inappropriate urinary potassium loss (> 35 mmol/24hr).

Patient Preparation

Drugs that interfere with the aldosterone / renin axis must be discontinued for 2 weeks prior to testing.

Effects of some drugs on renin and aldosterone

Patients should ideally not be on any medication listed for 2 weeks prior to test.  Aldosterone/renin ratios are less susceptible to interference, but those drugs asterisked must be avoided

Drug group Examples

Effect on renin

Effect on aldosterone

Comments
Non-steroidal anti-inflammatory drugs (NSAIDs) Aspirin, ibuprofen, indomethacin

-

Generally consistent effect, probably mediated via renal prostaglandins
*b -Blockers Atenolol, carvedilol, metoprolol, propranolol Generally consistent effect
*Potassium-sparing diuretics Amiloride, spironolactone, trimterene Very large increases in renin observed
*ACE inhibitors Captopril, cilazapril, enalapril, fosinopril, lisinopril, perindopril, ramipril Consistent and large increases in renin nearly always seen; effects on aldosterone inconsistent.
Thiazide diuretics Chlorthalidone, hydro-chlorothiazide, metolazone, xipamide Generally consistent effect with renin; more variable with aldosterone
Loop diuretics Frusemide Only small changes seen; effect on aldosterone variable
*Calcium channel antagonists Felodipine, licidipine, nicardipine, nifedipine ↑↓

None

↑↓

None

Very variable effects; significant increases and decreases have been reported, as well as no significant differences
Laxatives Most types when used in excess Probably linked to dehydration with abuse

The use of the renin:angiotensin ratio has largely replaced the need for patients to have been recumbent before the test.

Turnaround Time

1 month

Specimen

Lithium heparin plasma (Two samples required) for Renin & Aldosterone levels, plus a SST serum sample for U&E and Bicarbonate levels

Volume

2 ml plasma (aldosterone), 5ml plasm (renin), 2ml serum (U&E, Bicarb)

Container

Vacutainer green top

Vacutainer green top

Vacutainer gold top

Collection

Samples must be transported to laboratory immediately

Lab Handling

Sent to referral laboratory (Charing Cross)

Causes for Rejection

Unlabelled or incorrectly labelled sample; not meeting specific criteria for analysis; delay in sample reaching laboratory or in wrong sample container

Reference Range

See laboratory report for ranges and interpretation