Aetiology of hypertension (primary hyperaldosteronism, and other mineralocorticoid excess states associated with high blood pressure, renal artery stenosis, renin secreting tumours). Best done in conjunction with measurement of plasma aldosterone.
Localising renal ischaemic disease (renal vein renin sampling).
Diagnosis of primary adrenocortical insufficiency and assessing adequacy of mineralocorticoid replacement.
Diagnosis of Bartter's syndrome.
Diagnosis of hypovolaemic disorders (eg patients presenting with hyponatraemia, postural hypotension etc).
Diagnosis of hyporeninaemic syndromes.
Patient's posture, salt intake, drug therapy, age and time of sampling affect levels. Potassium depletion and/or hypokalaemia lower renin - aldosterone secretion.
Outpatients are best screened as follows: If possible stop non-essential anti-hypertensives for 2 weeks before sampling. Many hypotensive drugs alter renin - aldosterone levels; preferred agents are Alpha-blockers (Doxazosin, Prazosin) and non-dihydropyridine calcium channel blockers (Verapamil, Diltiazem) since they do not greatly alter renin - aldosterone. Screening tests for primary hyperaldosteronism and related conditions can still be done in patients on betablockers, ACE inhibitors and/or diuretics, BUT interpretation must allow for the potent effects these drugs have on the renin - aldosterone axis. Patients should attend (non-fasting) prior to 10.00 am for "ambulant sampling of plasma aldosterone and renin. It is usually wise to check plasma Na, K and creatinine at the time of sampling.
Inpatients are screened as above and should be ambulated for at least 30 minutes before sampling.
Other protocols involving plasma aldosterone/renin measurement include saline suppression (2L saline over 4 hours), 4-hour posture test (08.00 overnight supine aldosterone, repeated after 4 hr of upright posture) and tests using ACTH stimulation or dexamethasone suppression.
If patient is on high dose Biotin therapy (>5 mg/day), wait until at least 8 hours after last dose to take blood sample.
Specimen Collection Protocols:
EDTA blood collected and centrifuged at room temperature. Plasma stored and transported deep-frozen. Whole blood EDTA is stable for 8 hours at room temperature. Separated EDTA plasma is stable for 5 days at room temperature.
Thawed samples will not be assayed. If Renin or Aldosterone-Renin ratio is required, preferably collect blood before 10 am.
For Renin alone collect 1.5 ml (paediatric 1.2 ml).
Deliver to lab immediately.
If overnight - Frozen
Aliquot Instructions - Minimum 0.6 ml EDTA plasma for Renin alone or 1.0 ml for Aldosterone - Renin ratio. Snap frozen.
Send frozen. DO NOT STORE OR TRANSPORT AT 4oC due to cryoactivation of prorenin
to be inserted
07.00 – 10.00 Ambulant (adult): 5.3 – 99.1 mIU/L
07.00 – 10.00 Supine (adult): 4.2 – 59.7 mIU/L
$42.75 (Exclusive of GST)
Plasma must be frozen quickly because prorenin is activated at low (non-frozen) temperatures.
The sooner after bleeding the blood sample can be centrifuged at room temperature and snap frozen, the more reliable the result.
Other protocols involving Renin measurement include frusemide challenge, 2 hours of quiet standing or response to sodium depleting diets. Consult with an Endocrinologist for indications and test protocols.
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