Adrenal venous sampling in primary aldosteronism: a low dilution of adrenal venous blood is crucial for a correct interpretation of the results

OBJECTIVE: In primary aldosteronism, adrenal venous sampling (AVS) is essential for subtype differentiation as it evaluates aldosterone secretion from both adrenals. Selectivity of adrenal sampling is assessed by the ratio of cortisol concentrations in adrenal venous blood and inferior vena cava blood (C(adrenal)/C(ivc)). Since the criteria for selective adrenal sampling differ among the reported literature, we performed a study to evaluate the influence of different selectivity criteria on AVS results. DESIGN AND METHODS: Reports of AVS were screened retrospectively. All AVS were performed with cosyntrophin infusion. Reports containing samples with C(adrenal)/C(ivc)≥10 taken from both adrenals and at least one other adrenal sample characterised by C(adrenal)/C(ivc)≥1.1 were enrolled. For each individual, we chose reference samples that were defined by the highest C(adrenal)/C(ivc) achieved from each adrenal. The significance of the remaining samples with C(adrenal)/C(ivc)≥1.1 was analysed in regard to their respective reference samples. We assessed the impact of analysed samples on identification of lateralisation of aldosterone secretion that is crucial for decisions concerning adrenalectomy. RESULTS: AVS reports of 87 patients were enrolled. A total of 225 adrenal samples were analysed and divided into five groups according to C(adrenal)/C(ivc):1.1–1.99, 2–2.99, 3–4.99, 5–9.99 and ≥10. By comparing reference with analysed samples, a concordant assessment with respect to lateralisation of aldosterone secretion was observed in 39, 52, 72, 85 and 94% of the respective groups of analysed samples. CONCLUSION: AVS provides consistent information when adrenal samples with high cortisol concentrations are used.