Adrenal Vein Sampling Lab Analysis and Interpretation

Introduction The analysis and interpretation of laboratories from adrenal vein sampling (AVS) determine the procedure's success and the patient's candidacy for adrenalectomy. In primary aldosteronism (PA), the primary adrenal hormones measured are aldosterone and cortisol. Various indices are then calculated to guide management. Since adrenal glands do not secrete equal amounts of hormones, absolute values of aldosterone alone cannot be directly compared. One adrenal gland may inherently secrete more hormone than the other. Additionally, the left adrenal gland is commonly sampled at the adrenophrenic trunk, where the left adrenal vein (AV) merges with the left inferior phrenic vein, and adrenal hormone levels may be diluted by phrenic vein inflow. The right AV is sampled directly, and hormone levels are not diluted. Therefore, aldosterone levels from each adrenal gland are normalized to a reference hormone, such as cortisol, for comparison. Analysis of the samples involves calculating various indices, including the Selectivity Index (SI), Lateralization Index (LI), Contralateral Suppression Index (CSI), and/or Relative Aldosterone Secretion Index (RASI). These indices are compared with commonly accepted thresholds for interpretation. Currently, there are no established standard thresholds for interpreting AVS results. Numerous observational and retrospective studies have reported a wide range of thresholds and cutoffs with varying sensitivities and specificities based on pathological, clinical, and/or biochemical outcomes after adrenalectomy. Due to the lack of large prospective trials, index thresholds have largely been recommended by guidelines from expert consensus panels or societal working groups ([ Table 1 ]).[ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] Table 1 Adrenal vein sampling indices Index Formula Common cutoffs Interpretation Selectivity Index (SI) See Equation 1 ≥2 without stimulation ≥5 with stimulation Successful adrenal vein cannulation Lateralization Index (LI) See Equation 2 >2 without stimulation[ a ] >4 with stimulation Positive laterality for unilateral primary aldosteronism Contralateral Suppression Index (CSI) See Equation 3 <1 Optional, confirmation of laterality Relative Aldosterone Secretion Index (RASI) See Equation 4 Range, no consensus Optional, relatively new, may be helpful in borderline or partially successful cases a Note that the recent guidelines by the European Society of Hypertension and the Endocrine Society suggest LI > 4 for unstimulated sampling.[ 3 ] [ 20 ] Publication History Received: 29 January 2026 Accepted: 16 June 2026 Article published online: 09 July 2026 © 2026. Thieme. All rights reserved. Thieme Medical Publishers, Inc. 333 Seventh Avenue, 18th Floor, New York, NY 10001, USA