Suppressed Renin Values in Primary Aldosteronism Screening
Renin is considered suppressed when plasma renin activity (PRA) is <1.0 ng/mL/h or direct renin concentration (DRC) is <10 mIU/L (or <2 mU/L by some assays). 1
Understanding Renin Suppression Thresholds
The definition of suppressed renin varies slightly depending on the measurement method used:
By Plasma Renin Activity (PRA):
By Direct Renin Concentration (DRC):
Clinical Context and Interpretation
The key diagnostic principle is that primary aldosteronism demonstrates renin-independent aldosterone production, meaning aldosterone remains elevated despite suppressed renin 1, 4. This suppressed renin is the hallmark finding that distinguishes PA from other causes of hypertension.
Important Nuances:
When renin is suppressed, the aldosterone level matters significantly:
- Most guidelines require plasma aldosterone ≥10 ng/dL (277 pmol/L) by immunoassay when renin is suppressed to consider the screening positive 1
- The 2025 Endocrine Society guideline notes that with overt biochemical evidence (PRA <0.2 ng/mL/h or DRC <2 mU/L AND aldosterone >15 ng/dL by LC-MS/MS or >20 ng/dL by immunoassay), confirmatory testing may not even be required 4
Aldosterone-to-Renin Ratio (ARR) Cutoffs:
When using the ARR for screening with suppressed renin, the recommended thresholds are 5:
| Renin Method | ARR Threshold (Higher Sensitivity) | ARR Threshold (Higher Specificity) |
|---|---|---|
| PRA (ng/mL/h) | 555 pmol/L/ng/mL/h | 750 pmol/L/ng/mL/h |
| DRC (mIU/L) | 60 pmol/L/mIU/L | 91 pmol/L/mIU/L |
| DRC (ng/L) | 100 pmol/L/ng/L | 144 pmol/L/ng/L |
The 2025 AHA/ACC guideline uses a simpler ARR cutoff of 30 when aldosterone is in ng/dL and PRA in ng/mL/h, though acknowledges alternative thresholds of 20 or 40 1.
Common Pitfalls to Avoid
Don't dismiss PA based on "normal" aldosterone levels. Recent evidence shows that 45-67% of PA patients have aldosterone <20-30 ng/dL 6. The suppressed renin is the critical finding—even with aldosterone in the "normal" range, if renin is suppressed, PA remains possible.
Medication effects matter but shouldn't prevent initial screening. Beta-blockers and central alpha-agonists can suppress both renin and aldosterone, potentially causing false-positive results 1, 4. However, current guidelines support screening patients on their current medications, with repeat testing after medication withdrawal only if initial results are equivocal 1.
Rare cases of PA exist with unsuppressed renin. While uncommon, some PA patients (particularly those with concurrent cortisol excess) may have PRA >1.0 ng/mL/h 7. These patients tend to have higher cortisol levels and lower surgical success rates, but PA should not be completely ruled out by unsuppressed renin alone in highly suspicious cases.
In chronic kidney disease, renin decreases proportionately to nephron loss, leading to higher false-positive rates 4. Interpret screening results cautiously in this population.