Renin Activity, Plasma (PRA)

Marshfield Lab Public WebSite

Marshfield Clinic Public WebSite

Test Code: PRASO

Overview
Ordering
Specimen
Performing
Clinical/Interpretive
Contacts
Coding

Synonyms/Keywords

Renin Activity, Plasma

Useful For

Investigation of primary aldosteronism (eg, adrenal adenoma/carcinoma and adrenal cortical hyperplasia) and secondary aldosteronism (renovascular disease, salt depletion, potassium loading, cardiac failure with ascites, pregnancy, Bartter syndrome).

Specimen Requirements

Fasting Required	Specimen Type	Preferred Container/Tube	Acceptable Container/Tube	Specimen Volume	Specimen Minimum Volume (allows for 1 repeat)	Pediatric Minimum Volume (no repeat)
No	Plasma	Chilled, EEDTA Lavender Top Tubes (LTT)		2.0 mL	1.15 mL

Collection Processing Instructions

1. Draw blood in a chilled syringe from a patient in a seated position; place specimen in a chilled, lavender-top (EDTA) tube; and mix.

2. Alternatively, draw blood directly in a chilled, lavender top (EDTA) tube.

3. Immediately place EDTA tube into an ice-water bath until thoroughly cooled.

4. Refrigerate specimen during centrifugation and immediately transfer plasma to plastic vial. (If a refrigerated centrifuge is unavailable, chill the centrifuge carriers. Centrifuge specimen for < or =5 minutes, then promptly transfer plasma.)

5. Immediately freeze plasma.

Specimen Stability Information

Specimen Type	Temperature	Time
EDTA Plasma	Frozen	14 days

Rejection Criteria

Gross Hemolysis

Performing Laboratory Information

Performing Location	Day(s) Test Performed	Analytical Time	Methodology/Instrumentation
Mayo Medical Laboratory	Monday through Friday	2 days	Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Portions of this test are covered by patents held by Quest Diagnostics

Reference Lab

Mayo Clinic Laboratories

Test Information

The plasma renin activity cannot be interpreted if the patient is being treated with spironolactone (Aldactone). Spironolactone (Aldactone) should be discontinued for 4 to 6 weeks before testing.

Angiotensin converting enzyme (ACE) inhibitors have the potential to "falsely elevate" PRA. Therefore, in a patient treated with an ACE-inhibitor, the findings of a detectable PRA level or a low SA/PRA ratio do not exclude the diagnosis of primary aldosteronism. In addition, a strong predictor for primary aldosteronism is a PRA level undetectably low in a patient taking an ACE-inhibitor.

Not useful for determination of plasma renin concentration.

This test should not be requested in patients who have recently received radioisotopes, therapeutically or diagnostically, because of potential assay interference. A recommended time period before collection cannot be made because it will depend on the isotope administered, the dose given and the clearance rate in the individual patient. Specimens will be screened for radioactivity prior to analysis. Radioactive specimens received in the laboratory will be held and assayed after the radioactivity has sufficiently decayed. This will result in a test delay.

Reference Range Information

Performing Location	Reference Range
Mayo Medical Laboratories	0-2 years: 4.6 ng/mL/hour (mean)* Range: 1.4-7.8 ng/mL/hour 3-5 years: 2.5 ng/mL/hour (mean)* Range: 1.5-3.5 ng/mL/hour 6-8 years: 1.4 ng/mL/hour (mean)* Range: 0.8-2.0 ng/mL/hour 9-11 years: 1.9 ng/mL/hour (mean)* Range: 0.9-2.9 ng/mL/hour 12-17 years: 1.8 ng/mL/hour (mean)* Range: 1.2-2.4 ng/mL/hour Mean data not standardized as to time of day or diet. Infants were supine, children sitting. Na-depleted, upright (peripheral vein specimen) 18-39 years: 10.8 ng/mL/hour (mean) 2.9-24.0 ng/mL/hour (range) > or =40 years: 5.9 ng/mL/hour (mean) 2.9-10.8 ng/mL/hour (range) Na-replete, upright (peripheral vein specimen) 18-39 years: 1.9 ng/mL/hour (mean) < or =0.6-4.3 ng/mL/hour (range) > or =40 years: 1.0 ng/mL/hour (mean) < or =0.6-3.0 ng/mL/hour (range) *Stalker HP, Holland NH, Kotchen JM, Kotchen TA: Plasma renin activity in healthy children. J Pediatr 1976;89:256-258

Performing Location

Reference Range

Mayo Medical Laboratories

0-2 years: 4.6 ng/mL/hour (mean)* Range: 1.4-7.8 ng/mL/hour

3-5 years: 2.5 ng/mL/hour (mean)* Range: 1.5-3.5 ng/mL/hour

6-8 years: 1.4 ng/mL/hour (mean)* Range: 0.8-2.0 ng/mL/hour

9-11 years: 1.9 ng/mL/hour (mean)* Range: 0.9-2.9 ng/mL/hour

12-17 years: 1.8 ng/mL/hour (mean)* Range: 1.2-2.4 ng/mL/hour

Mean data not standardized as to time of day or diet. Infants were supine, children sitting.

Na-depleted, upright (peripheral vein specimen)

18-39 years: 10.8 ng/mL/hour (mean)

2.9-24.0 ng/mL/hour (range)

> or =40 years: 5.9 ng/mL/hour (mean)

2.9-10.8 ng/mL/hour (range)

Na-replete, upright (peripheral vein specimen)

18-39 years: 1.9 ng/mL/hour (mean)

< or =0.6-4.3 ng/mL/hour (range)

> or =40 years: 1.0 ng/mL/hour (mean)

< or =0.6-3.0 ng/mL/hour (range)

*Stalker HP, Holland NH, Kotchen JM, Kotchen TA: Plasma renin activity in healthy children. J Pediatr 1976;89:256-258

Interpretation

A high ratio of serum aldosterone (SA) in ng/dL to plasma renin activity (PRA) in ng/mL per hour, is a positive screening test result, a finding that warrants further testing. A SA/PRA ratio > or =20 and SA > or =15 ng/dL indicates probable primary aldosteronism.

Renal disease, such as unilateral renal artery stenosis, results in elevated renin and aldosterone levels. Renal venous catheterization may be helpful. A positive test is a renal venous renin ratio (affected/normal) >1.5.

Outreach CPTs

CPT	Modifier (if needed)	Quantity	Description	Comments
84244