RENIN ACTIVITY PLASMA

General Information

HLAB/HOL Code: REN
UPHSM LIS Test #: 6690
Schedule:
Testing Time:
Testing Lab: Labcorp

Specimen Info
Only 1 specimen type required, unless otherwise specified

Volume: 3 mL(2mL min)
Temperature: Frozen
Tube Type: Plasma, Frozen
Collection Info:
Container:  Lavender-top (EDTA) tube

Special Instructions:  The patient's posture at the time of collection should be noted (see Patient Preparation).

Collection:  Draw blood into an EDTA tube. Keep tube at room temperature. Centrifuge at room temperature.1 Transfer the plasma into a plastic transfer tube with screw cap. Freeze immediately and maintain frozen until tested. It is critical that the plasma be transferred and frozen as quickly as possible to prevent cryoactivation of protein to renin (which results in falsely elevated renin levels). To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions:  Freeze

Patient Preparation:  In order to facilitate interpretation of test results, the patient should be taken off medications for at least three weeks prior to sample collection. Dietary sodium levels during the period prior to testing can affect renin levels. Sodium restriction tends to cause an increase in renin activity, while supplementation can result in lower values. A 24-hour urine sodium determination from a sample collected on the day before a renin test can be used to assess sodium intake. Expected renin activity levels for various levels of urinary sodium excretion are provided. Renin activity determination without the concurrent urine sodium measurement can still provide useful information if the clinician verifies that the patient has been on a normal sodium diet.

Since patient posture prior to collection affects renin levels, it is recommended that the patient be ambulatory for at least 30 minutes before blood collection.  If inpatients are physically able, they should be asked to ambulate for 30 minutes before blood is drawn for renin activity. Reference intervals are provided for patients who have ambulated for at least 30 minutes prior to collection (upright patients). Reference intervals are also provided for patients on a normal sodium diet who are unable to ambulate (supine patients).

Causes for Rejection:  Gross hemolysis; serum or heparinized plasma specimen; specimen not received frozen; recently administered isotopes

Methods

Radioimmunoassay

Clinical Utilities

Use:  Measurement of renin activity is useful in the differential diagnosis of individuals with hypertension. Renin levels will be elevated in patients with hypertension due to renal artery stenosis (ie, renovascular hypertension). Measurement of renin activity can also be useful in the diagnosis of primary aldosteronism. Patients with secondary aldosteronism tend to have low renin levels. Renin can also be used to assess the adequacy of steroid substitution in patients with adrenal insufficiency. Renin activity will be normal in patients with adequate supplementation and will be elevated when steroid substitution is inadequate.

Limitations:  Random samples may be difficult to interpret unless medications and state of sodium balance are defined. Interpretation of results may be difficult if patient is on antihypertensive drugs, cyclic progestogens, estrogens, diuretics, or licorice. Upright posture, administration of diuretics, low sodium diets stimulate renin release. Indomethacin lowers plasma renin activity. Salicylates decrease renin levels; on cessation of therapy, renin levels rise above normal before return to normal.

CPT Codes

84244

* The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding
is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.

Reference Range

See Report