Context: The assessment of selectivity of blood sampling is a fundamental step for a proper interpretation of the results of adrenal vein sampling (AVS), which is a "must" for identifying the surgically curable subtypes of primary aldosteronism. However, uncertainties remain on how to best achieve this goal.
Objective: The aim of the study was to investigate whether chromogranin A (ChA) is tonically released in adrenal vein blood and might be used to assess the selectivity of AVS.
Design and methods: In consecutive patients undergoing AVS, we compared the plasma cortisol and ChA levels in the adrenal veins and infrarenal inferior vena cava blood. We then calculated and compared the selectivity index based on cortisol with that based on ChA.
Results: Thirteen patients had cortisol and ChA levels assessed simultaneously. Besides the expected step-up of cortisol, they showed a step-up of ChA levels between the inferior vena cava and blood from either adrenal vein. The selectivity index determined with ChA was weakly correlated with that calculated with cortisol; the former was much smaller (3- and 4- fold on the right and left side, respectively) than the latter. This translated into a proportional error at Bland-Altman plot between selectivity indexes. Accordingly, only 53% of AVS were bilaterally selective using the selectivity index determined with ChA, as compared to 84% with selectivity index determined with cortisol (P = 0.0001).
Conclusions: These findings indicate that ChA is tonically released by the adrenal gland but do not support the usefulness of using ChA instead of cortisol for assessing the selectivity of blood sampling during AVS, perhaps with the exception of aldosterone-producing tumors that cosecrete cortisol.