The plasma renin activity test (PRA)

A clinical test for defining low, medium and high renin hypertension.

Conditions for drawing and processing blood
Blood is drawn into an EDTA, lavender top Vacutainer from a quietly seated patient under the usual doctor’s office or clinic conditions. Blood is centrifuged at ambient temperature. Then, the plasma is separated, frozen and sent to the laboratory.

Defining low, medium and high PRA levels:
30% of hypertensive patients have low PRA, 60% have medium PRA, about 10% have high PRA.

PRA definitions (ng/ml/hr) for patients not taking an ACEI or ARB:
Low renin: < 0.65
Medium renin: 0.65 – 4.5
High renin: > 4.5
PRA and effective PRA (ePRA)* (ng/ml/hr) definitions during ACEI or ARB treatment:
Low renin: < 6.5  (< 0.65)
Medium renin: 6.5 – 45 (0.65 – 4.5)
High renin:  > 45 (4.5)

* ePRA (effective PRA) = 0.1 x PRA. Plasma renin-angiotensin system activity is blocked by about 90% in patients taking an ACEI or ARB.

  1. Sealey JE. Plasma renin activity and plasma prorenin assays. Clin Chem 1991;37(10 Pt 2):1811-9.
  2. Laragh JH, Sealey JE. The plasma renin test reveals the contribution of body sodium-volume content and renin-angiotensin vasoconstriction to long term blood pressure. Am J Hypertens 2011;24:1164-1180