Plasma Renin Activity

The Plasma Renin Activity (PRA) test measures the functional activity of renin, an enzyme produced by the kidneys that plays a central role in the Renin-Angiotensin-Aldosterone System (RAAS), which regulates blood pressure, fluid balance, and electrolytes. When blood pressure or sodium levels fall, the kidneys release renin, triggering a cascade that produces angiotensin II and aldosterone, leading to blood vessel constriction and sodium and water retention, thereby increasing blood pressure. Unlike a direct renin concentration test, PRA measures the amount of angiotensin I generated over time, providing a dynamic assessment of RAAS activity. It is an important tool for evaluating hypertension, adrenal disorders, and electrolyte imbalances.

Who should get this test done?

This test is recommended for individuals who:

●     Have treatment-resistant or difficult-to-control hypertension.

●     Develop hypertension before age 30, suggesting a possible secondary cause.

●     Have high blood pressure with unexplained low potassium (hypokalemia).

●     Have chronic kidney disease (CKD) with associated hypertension.

●     Have a family history of hypertension, adrenal, or endocrine disorders affecting blood pressure.

Why consider this test?

Measuring Plasma Renin Activity (PRA) helps evaluate the hormonal regulation of blood pressure and identify underlying causes of hypertension. This test helps:

●     Identify the cause of hypertension – Differentiates primary hypertension, renovascular hypertension, and primary aldosteronism.

●     Diagnose primary aldosteronism (Conn’s syndrome) – Low PRA with high aldosterone levels and an elevated Aldosterone-to-Renin Ratio (ARR) are key diagnostic findings.

●     Evaluate renovascular hypertension – High PRA may indicate renal artery stenosis causing excess renin release.

●     Guide antihypertensive therapy – Helps select the most effective blood pressure medications based on renin status.

●     Monitor treatment response – Tracks outcomes of adrenal surgery, renal artery interventions, and RAAS-targeted therapies.

More Information

PRA is most informative when measured alongside serum aldosterone. The Aldosterone-to-Renin Ratio (ARR) is the primary screening test for primary aldosteronism (Conn’s syndrome), where low PRA and high aldosterone indicate autonomous aldosterone production. Renin profiling also helps guide antihypertensive therapy: high-renin hypertension responds better to ACE (Angiotensin-Converting Enyme) inhibitors  or ARBs(Angiotensin II receptor blockers), while low-renin hypertension responds better to diuretics or calcium channel blockers. Since many medications can significantly affect renin levels, proper preparation and physician-guided medication adjustments are essential for accurate results.

Other names:

●     PRA Test

●     Renin Activity Test

●     Plasma Renin Test

●     Renin - Angiotensin System Test

●     Serum Renin Test

●     Renin Assay