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

Abstract

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

Design: 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).

Setting: A hypertension clinic in a large teaching hospital.

Patients and results: 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.

Conclusions: 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.