부산대학교 도서관

OBJECTIVE:: Primary aldosteronism (PA) is characterized by excessive, autonomous secretion of aldosterone which fails to suppress upon administration of fludrocortisone and/or salt loading. Seated saline suppression testing (SSST; 2L of normal saline infused over 4 h while seated) was recently reported to be superior to recumbent (RSST)1. The recommended diagnostic cut-off 4 h plasma aldosterone level (162 pmol/L) for SSST was based on that measured by HPLC-MS/MS. Most diagnostic laboratories, however, use immunoassays to measure aldosterone.The aim of this study is to define the optimal cut-off plasma aldosterone level measured by immunoassay for the diagnosis of PA using SSST. DESIGN AND METHOD:: This study involved 80 of the 85 subjects (insufficient remaining plasma samples in the other 5) whose data were used for receiver operating characteristic (ROC) analysis to define the optimal HPLC-MS/MS plasma aldosterone cut-off in the original study1. Of these, PA was confirmed in 65 (23 unilateral, 34 bilateral and 8 subtype yet to be determined) by positive fludrocortisone suppression testing (FST) and/or lateralization on adrenal venous sampling and excluded in 15 (12 cured of PA post-adrenalectomy and 3 non-PA) by negative FST. Aldosterone concentration was measured in the plasma samples collected during SSST by a chemiluminescence immunoassay using the DiaSorin Liaison XL analyser. RESULTS:: ROC analysis revealed an optimal diagnostic cut-off 4 h plasma aldosterone level of 171 pmol/L when measured by the immunoassay (AUC = 0.893; P < 0.001). The sensitivity and specificity for diagnosis of PA at this cut-off were 95.4% and 80.0% respectively (Youden index =0.754). None of the three subjects with false-negative SSST had unilateral PA. There was a strong correlation between the plasma aldosterone concentrations measured by immunoassay and those by HPLC-MS (Pearson correlation coefficient r = 0.94, P < 0.001). CONCLUSIONS:: SSST is a highly sensitive test for the diagnosis of PA. A higher diagnostic cut-off level should be employed when plasma aldosterone level is analyzed by immunoassay compared to that by HPLC-MS/MS.