Assessment of the Selectivity and Lateralisation Index for Adrenal Vein Sampling in Primary Aldosteronism

Introduction: Adrenal vein sampling (AVS) is crucial for identifying the primary aldosteronism (PA) subtypes, but the cut-off values for ascertaining selectivity of catheterisation and lateralisation of aldosterone secretion remain controversial. The aims of our study were: 1) to evaluate the cut-off values for the Selectivity (SI) and Lateralisation Index (LI) in patients with aldosterone-producing adenoma (APA); 2) to examine the effect of ACTH stimulation on SI and LI performance. Methods: We assessed the proportion of selective AVS at different SI cut-off values in 150 consecutive patients with PA undergoing bilaterally simultaneous AVS. APA diagnosis required: 1) biochemical evidence of PA; 2) lateralisation of aldosterone secretion; 3) adenoma at pathology, and 4) normocalaemia + correction of PA + cure or improvement of hypertension at follow-up. In 39 patients with bilaterally selective AVS and APA by these criteria we examined different cut-off values of LI for assessing the lateralisation of aldosterone excess and the usefulness of ACTH stimulation (250 μg i.v. bolus) in improving SI and LI during AVS. Results: Bilaterally selective AVS decreased steadily (from 79.2% to 39.6%) by increasing SI cut-offs from 1.1 to 5.0. Likewise, correctly identified APAs fell (from 97.4% to 43.6%) by increasing LI cut- offs from 1.125 to 5.0. ACTH improved the assessment of selectivity, but exerted a confounding effect on LI. Conclusions: 1) Increasing the SI cut-offs lowers the number of usable AVS. 2) Higher LI cut-off values lead to overlooking of a proportion of APAs. 3) The improved selectivity with ACTH stimulation should be weighed against the loss of correct lateralisation.