Morning plasma aldosterone predicts the subtype of primary aldosteronism independent of sodium intake.

The objective of the present study was to assess the potential predictive value of supine morning plasma aldosterone concentration, a component of the postural stimulation test (PST), in distinguishing aldosterone-producing adenoma (APA) from idiopathic adrenal hyperplasia (IAH) in a series of 61 patients with confirmed primary aldosteronism (PAL). The reproducibility of the PST was also tested under conditions of both normal- and high-sodium intake. Twenty-seven patients had surgery-confirmed unique APA. Thirty-four patients were classified as IAH and treated medically. Morning plasma aldosterone values were significantly higher in patients with APA compared to those with IAH (p < 0.01) on both diets. Using the receiver-operating characteristic (ROC) curve analysis, it was observed that the cutoff values in the highest (>900 pmol/L or 32 ng/dl) and lowest (<300 pmol/L or 11 ng/dl) range of the morning plasma aldosterone measurements were predictive of the subtype diagnosis in about 50% of PAL cases (31 of 61 patients). The sensitivity, specificity, and accuracy of the PST were >70% on both sodium diets. The PST was also reproducible irrespective of sodium intake. Moreover, one of its components, the supine morning plasma aldosterone, can be used as an indicator for the subtype diagnosis in about half of PAL patients.