Response to “Effective” Plasma Renin Activity: A Derived Measure for Assessing Residual Plasma Renin Activity in Patients Taking Angiotensin-Converting Enzyme Inhibitors or Angiotensin Receptor Blockers

We thank Sealey et al 1 for their interest in our article and their comments. They point out that plasma renin activity (PRA) in our study likely overestimated the true activity of circulating PRA and, by calculating the effective PRA, our results would be predictable. Suppressed PRA is a marker of volume overload and can occur with high dietary salt ingestion. Theoretically, patients with suppressed PRA might achieve greater blood pressure (BP) reductions with a low-salt diet than patients with high PRA because of greater salt sensitivity. Some investigators, but not all, have reported that low levels of renin predict the magnitude of BP reduction secondary to sodium depletion. As discussed in our report, 4 Gavras et al 5 demonstrated extreme BP reductions during a low-salt diet (10 mmol) and high doses of diuretics. They reported that a small percentage of rise in PRA was a better predictor of BP reduction than initial renin levels alone. In the same study, 1 patient in whom PRA at baseline was 70 ng/mL per hour had his BP decreased by 38/18 mm Hg after sodium reduction of 206 mmol. In another patient, PRA was 0.58 ng/mL per hour, and BP decreased by 21/1 mm Hg after a 404-mmol reduction in sodium. These individual results highlight that PRA is not the only determinant of BP response, and even patients with high renin levels can achieve large BP reductions with a low-salt diet.