Ratio of serum aldosterone to plasma renin concentration in essential hypertension and primary aldosteronism

The ratio of serum aldosterone to plasma renin activity (PRA) has been proposed as sensitive screening method in the diagnosis of primary aldosteronism under random conditions. However, the method for determination of renin activity is hampered by the necessity of ice cooling during storage and transport. The present study was therefore conducted to examine the ratio of serum aldosterone to plasma renin concentration (ARR) and its usefulness in diagnosis of primary aldosteronism under ambulatory conditions and given anti hypertensive medication. 146 patients with arterial hypertension who consecutively attended the outpatient clinic were studied prospectively. Patients with secondary hypertension besides primary aldosteronism were not included in the series. 37 normotensive patients served as control. Also, 17 patients with known primary aldosteronism were retrospectively examined. Among the hypertensive group 2 patients with Conn's syndrome were newly detected (1.4%). ARR was 7.92 +/- 6.04 [pg/ml/[pg/ml] in normotensive controls (range from 2.03 to 26.98), 14.61 +/- 18.50 [pg/ml]/[pg/ml] in patients with essential hypertension (n = 144, range from 0.41 to 115.45) and 155.92 +/- 127.84 [pg/ml]/[pg/ml] in patients with primary aldosteronism (n = 19, range from 6.75 to 515). 17 of the 19 patients with Conn's syndrome had an ARR of more than 50. Under ongoing drug treatment this represents a sensitivity of 89% and a specificity of 96%. Sensitivity decreased to 84% and specificity increased to 100% when a second criteria (alclosterone greater than or equal to200pg/ml) was included. In summary, ARR using renin concentration is a useful screening parameter for primary aldosteronism.