Prevalence and Clinical Manifestations of Primary Aldosteronism
What is the prevalence and clinical phenotype of primary aldosteronism (PA) in a large cohort of unselected patients referred to a hypertension clinic by general practitioners?
Following withdrawal from all interfering medications, patients in a Torino, Italy referral center were screened for PA using the ratio of serum aldosterone to plasma renin activity (ARR). PA was diagnosed according to Endocrine Society guidelines. Diagnosis was confirmed or excluded by an intravenous saline infusion test or captopril challenge test, and subtype differentiation was performed by adrenal computed tomography scanning and adrenal vein sampling (AVS), using strict criteria to define both successful cannulation and lateralization of aldosterone production.
A total of 1,672 primary care patients with hypertension—569 newly diagnosed and 1,103 patients already diagnosed with hypertension—were included in the study. A total of 99 patients (5.9%) were diagnosed with PA and conclusive subtype differentiation by AVS was made in 91 patients (27 patients with an aldosterone-producing adenoma and 64 patients with bilateral adrenal hyperplasia). The overall prevalence of PA increased with the severity of hypertension, from 3.9% in stage 1 hypertension to 11.8% in stage 3 hypertension. Patients with PA more frequently displayed target organ damage and cardiovascular events compared to those without PA, independent of confounding variables.
The results demonstrate that PA is a frequent cause of secondary hypertension, even in the general population of patients with hypertension, and indicates that the majority of these patients should be screened for PA.
The study provides an unbiased prevalence of PA in a single primary care referral center. That nearly 4% of stage 1 hypertensive patients have PA should encourage widespread screening. Treatments for hypertension including angiotension-converting enzyme inhibitor (ACEi)/angiotensin-receptor blocker (ARB), thiazide diuretics, and spironolactone can result in missing a large percentage of PA. The ARR cutoff level used in this study after correcting the low potassium and withholding ACEi/ARB and spironolactone was 30 ng/dl, together with an aldosterone level >10 ng/dl. Most authors recommend an ARR of 20-40 (with aldosterone >10-15 ng/dl). An ARR of at least 35 has 100% sensitivity and 92.3% specificity in diagnosing PA.
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