The aldosterone/renin ratio as a screening test for primary aldosteronism

To investigate the utility of random outpatient plasma aldosterone and renin measurements in screening for primary aldosteronism (PA) in hypertensive patients.

Clinical records of hypertensive patients who had aldosterone and renin determinations over a 3-year period were analysed retrospectively. The patients were arbitrarily classified into five groups defined according to the aldosterone level and the aldosterone/renin (A/R) ratio: PA (plasma aldosterone > 500, A/R ratio > or = 1,000; essential hypertension (EHT) (aldosterone < 1,000, A/R < 1000); secondary hyperaldosteronism (SHA) (aldosterone > or = 1,000, A/R < 400); low-renin hypertension (LRHT) (aldosterone < 500, A/R > or = 1,000); miscellaneous hyperaldosteronism (MHA) (aldosterone > or = 1,000, A/R 400-1000).

A hypertension clinic in a large teaching hospital.

The sample of 216 hypertensives were classified as follows: EHT 51%, LRHT 8%, PA 32%, SHA 7%, and MHA 3%. Mean plasma potassium values were significantly lower (P < 0.0001) in the PA group compared with essential hypertensives, but plasma K+ was of little utility in identifying individual patients with PA, as 71% were normokalaemic. Adrenal computed tomography scans were performed on 38 of 69 patients with PA, and revealed definite unilateral or bilateral adrenal masses in 7 and probable unilateral masses in a further 4. Five patients underwent unilateral adrenalectomy, confirming adrenal adenomas in 4 and nodular hyperplasia in 1. The minimum prevalence of PA due to adrenal adenoma or hyperplasia was 3.3% of all hypertensives and 10.1% of patients with biochemical PA defined by A/R ratio. Patients with biochemical PA had more target organ damage, and in general responded more favourably to regimens with spironolactone than to conventional therapy.

A random outpatient aldosterone and renin measurement identifies a group of hypertensives with biochemical PA in which there is a significant prevalence of adrenal adenomas, increased prevalence of target organ damage and a good response to spironolactone. These results have major implications for the investigation and management of patients with severe or resistant hypertension.