Patient Preparation: The plasma renin activity cannot be interpreted if the patient is being treated with spironolactone (Aldactone). Spironolactone should be discontinued for 4 to 6 weeks before testing.
Collection Container/Tube: Chilled, lavender top (EDTA)
Submission Container/Tube: Plastic vial
Specimen Volume: 2 mL
Collection Instructions:
Draw blood in a chilled syringe from a patient in a seated position; place specimenin a chilled, lavender-top (EDTA) tube; and mix
Alternatively, draw blood directly in a chilled, lavender top (EDTA) tube
Immediately place EDTA tube into an ice-water bath until thoroughly cooled
Refrigerate specimen during centrifugation and immediately transfer plasmato plastic vial. (If a refrigerated centrifuge is unavailable, chill the centrifuge carriers. Centrifuge specimen for ≤5 minutes, then promptly transfer plasma.)
Immediately freeze plasma
Stability
Frozen: 14 days
Unacceptable Specimen Conditions
Gross hemolysis
Limitations
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.
Methodology
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
