Eurofins Biomnis code

REN

Synonyms

• RAP
• Renin-angiotensin system activity
• Renin activity
• Endocrinology

Clinic significance

A proteolytic enzyme synthesized by renal juxtaglomerular cells which converts angiotensinogen into angiotensin I. Useful in the diagnosis of renovascular hypertension. Increased levels seen in high blood pressure and in response to certain drugs (diuretics and calcium inhibitors). Reduced levels are associated with primary hyperaldosteronism (Conn's syndrome) and hyperadrenocorticism (e.g. Cushing's syndrome).
The measured activity of the renin-angiotensin-aldosterone system (RAAS) depends on many different factors, including:
- the (position) posture of the subject: during sampling
* lying down: the subject should have been lying down and at rest for at least 3 hours without having so much as put a foot on the ground (blood to be drawn at the patient's home with a third party opening the door)
* standing up: slowly walking for at least one hour; both renin and aldosterone levels double in an erect posture;

- age: levels decrease with age . The concentration in 50 year-olds is about one half that observed in those of under 30 years of age
- sodium intake: RAAS activity is inversely related to sodium intake so it is essential to make sure the subject is not on any special diet with respect to sodium;
- drugs: most antihypertensive drugs interfere with RAAS activity. All diuretics, beta-blockers and converting enzyme inhibitors should have been discontinued at least two weeks before the test and aldosterone antagonists (e.g. spironolactone) should be discontinued a full month beforehand. Courses of prazosin (e.g. Minipress and Alpress LP) and of centrally acting antihypertensive drugs (e.g. methyldopa) can be continued.

Prenalytics

• 1 mL
• Plasma EDTA
• FROZEN

Further information

• DIET INFORMATION: our reference ranges are only valid for a normal salt intake (80-250mEq/24hrs natriuresis )
• Specify upright or reclined :
  Sampling in upright position after 1 hr of walking : REND
  Sampling in the reclined position after 1 hr in supine position : RENC
• Optimal sampling conditions according to SFE / SFHTA / AFCE: in the morning, more than 2 hours after waking up, in a sitting position after 5 to 15 minutes, with normal dietary salt intake, normal kalemia, and without antihypertensive drugs that significantly interfere with the renin-angiotensin-aldosterone system. Antihypertensive medications that can be maintained during exploration include alpha-blockers and calcium channel blockers.

Methodology

Radioimmunoassay

Turnaround time

3 days