EVALUATION OF THE DEXAMETHASONE SUPPRESSION TEST FOR THE DIAGNOSIS OFGLUCOCORTICOID-REMEDIABLE ALDOSTERONISM

Glucocorticoid-remediable aldosteronism (GRA) is a rare form of inheri ted hypertension caused by a characteristic gene duplication. With the advent of definitive genetic testing for GRA, the performance of the traditional screening test for GRA, the dexamethasone suppression test (DST), can be evaluated. We compared the DST to direct genetic testin g in 24 patients referred for genetic screening for GRA (12 GRA positi ve and 12 GRA negative) based on clinical and biochemical findings, DS T, and family history. Plasma aldosterone was measured before and afte r oral dexamethasone administration to determine the extent to which a ldosterone was suppressed by glucocorticoids in each patient group. Th e results of the DST in these subjects were also compared to those in 19 historical patients with primary aldosteronism [4 bilateral hyperpl asia and 15 aldosterone-producing adenoma (APA)] reported previously. The DST differentiated GRA-positive from GRA-negative patients with 92 % sensitivity and 100% specificity. Cutoffs based on the post-DST plas ma aldosterone level (<4 ng/dL) or percent suppression compared to bas eline (>80%) were equally effective in correctly diagnosing GRA (only one GRA-positive patient would have been incorrectly diagnosed). Howev er, DST in 15 APA patients revealed that 33% had greater than 80% supp ression of aldosterone, and 1 had aldosterone levels below 4 ng/dL. We conclued that a post-DST aldosterone level below 4 ng/dL will correct ly diagnose GRA patients with high sensitivity and specificity. Suppre ssion compared to baseline can be misleading, as evidenced by the resu lts in APA patients and referred subjects who genetically screened neg ative.