An Aldosterone/Renin Ratio of 1.8 is Normal and Does Not Suggest Primary Aldosteronism
Your aldosterone/renin ratio of 1.8 is well below the diagnostic threshold and effectively rules out primary aldosteronism as a cause of hypertension. This result requires no further workup for this condition unless other compelling clinical features emerge.
Understanding Your Result
The diagnostic cutoff for primary aldosteronism is an ARR ≥30 (when aldosterone is measured in ng/dL and plasma renin activity in ng/mL/h), and your ratio of 1.8 is far below this threshold 1, 2
For a positive screening test, not only must the ratio be elevated, but the plasma aldosterone concentration itself should be at least 10-15 ng/dL 1, 2
Your low ratio indicates that your renin and aldosterone are in appropriate proportion to each other, which is the expected finding in essential (primary) hypertension 1
What This Means Clinically
Primary aldosteronism is definitively excluded with this ratio, as the condition is characterized by inappropriately high aldosterone production with suppressed renin, resulting in ratios typically >30 1, 2
The specificity of the ARR improves when a minimum plasma renin activity of 0.5 ng/mL/h is used in calculations, but even accounting for this, your ratio remains well within normal limits 2
Studies demonstrate that ARR values this low have excellent negative predictive value for ruling out primary aldosteronism 3, 4
When to Reconsider Testing
You would only need repeat ARR testing if you develop:
Resistant hypertension (blood pressure not controlled on 3 medications including a diuretic) 1, 2
Spontaneous or significant diuretic-induced hypokalemia (potassium <3.5 mEq/L) 1, 2
An incidentally discovered adrenal mass on imaging performed for other reasons 1, 2
Family history of early-onset hypertension or stroke at young age (<40 years) 1, 2
Important Caveats About ARR Testing
Certain medications can affect the ARR: beta-blockers can falsely elevate it, while ACE inhibitors and ARBs can falsely lower it, though your low ratio makes this clinically irrelevant 2, 5
Testing should ideally be performed with the patient potassium-replete, as hypokalemia can suppress aldosterone production and lower the ratio 2, 6
Blood should be collected in the morning after the patient has been out of bed for 2 hours and seated for 5-15 minutes immediately before collection 2
No Further Action Required
Given your normal ARR of 1.8, no confirmatory testing (saline suppression test or oral salt loading) is needed, and referral to an endocrinologist or hypertension specialist is not indicated 1, 2. If hypertension is present, it should be managed as essential hypertension with standard antihypertensive therapy.