High prevalence of primary aldosteronism among black and white subjects with resistant hypertension

Recent reports suggest that primary aldosteronism (PA) may occur in up to 15% of hypertensive patients. To determine the prevalence of PA among patients with treatment-resistant hypertension, we evaluated 54 consecutive patients referred to UAB for resistant hypertension (requiring use of 3 or more antihypertensive agents). Subjects were maintained on prescribed antihypertensive therapies except for spironolactone, amiloride, or triamterene. Plasma aldosterone concentration (PAC; ng/dl), plasma renin activity (PRA; ng/ml/hr), and twenty-four hour urinary aldosterone excretion (mcg/24-hr) during high dietary salt ingestion (>200 meq/24-hr) were determined in each patient. The diagnosis of PA was confirmed in patients in whom the PRA was <1.0 and 24-hr urinary aldosterone excretion was >12. If unable to adequately complete a 24-hr urine collection, PA was confirmed by fludrocortisone suppression test (FST). High resolution CT of the adrenal glands was performed on every patient with biochemically confirmed PA. PA was confirmed in 13 of 54 or 24.1% of the patients. PA was diagnosed in 7 of 31 or 22.6% of the white subjects and 6 of 23 or 26.1% of African-American subjects. Three of the 13 patients with PA had adrenal adenomas by CT scanning. Compared to confirmatory testing by high dietary salt suppression of urinary aldosterone excretion or FST, the PAC/PRA ratio had a sensitivity of 92.3% and a specificity of 50.0%. Primary aldosteronism is a common cause of resistant hypertension among African-American and white subjects referred to a specialty clinic. We propose that the PAC/PRA ratio has sufficient sensitivity to screen for but lacks the specificity to confirm the diagnosis of PA. Therefore, PA should be evaluated for by assessment of twenty-four hour urinary aldosterone excretion or FST in all patients with resistant hypertension and a suppressed PRA (<1.0).