Endocrine Hypertension Research Centre, University of Queensland Diamantina Institute, Princess Alexandra Hospital, Brisbane, Australia.
Department of Endocrinology, Princess Alexandra Hospital, Brisbane, Australia.
J Clin Endocrinol Metab. 2020 Mar 1;105(3). doi: 10.1210/clinem/dgz150.
In primary aldosteronism (PA), excessive, autonomous secretion of aldosterone is not suppressed by salt loading or fludrocortisone. For seated saline suppression testing (SSST), the recommended diagnostic cutoff 4-hour plasma aldosterone concentration (PAC) measured by high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS is 162 pmol/L. Most diagnostic laboratories, however, use immunoassays to measure PAC. The cutoff for SSST using immunoassay is not known. We hypothesized that the cutoff is different between the assays.
We analyzed 80 of the 87 SSST tests that were performed during our recent study defining the HPLC-MS/MS cutoff. PA was confirmed in 65 by positive fludrocortisone suppression testing (FST) and/or lateralization on adrenal venous sampling and excluded in 15 by negative FST. PAC was measured by a chemiluminescence immunoassay (PACIA) in the SSST samples using the DiaSorin Liaison XL analyzer, and receiver operating characteristics (ROC) analysis was performed to identify the PACIA cutoff.
ROC revealed good performance (area under the curve = 0.893; P < .001) of 4-hour postsaline PACIA for diagnosis of PA and an optimal diagnostic cutoff of 171 pmol/L, with sensitivity and specificity of 95.4% and 80.0%, respectively. A higher cutoff of 217 pmol/L improved specificity (86.7%) with lower sensitivity (86.2%). PACIA measurements strongly correlated with PAC measured by HPLC-MS (r = 0.94, P < .001).
A higher diagnostic cutoff for SSST should be employed when PAC is measured by immunoassay rather than HPLC-MS/MS. The results suggest that (i) PA can be excluded if 4-hour PACIA is less than 171 pmol/L, and (ii) PA is highly likely if the PACIA is greater than 217 pmol/L by chemiluminescence immunoassay. A gray zone exists between the cutoffs of 171 and 217 pmol/L, likely reflecting a lower specificity of immunoassay.
在原发性醛固酮增多症（PA）中，醛固酮的过度、自主分泌不受盐负荷或氟氢可的松的抑制。对于坐姿盐水抑制试验（SSST），通过高效液相色谱-质谱法（HPLC-MS/MS 测量的推荐诊断截止值 4 小时血浆醛固酮浓度（PAC）为 162 pmol/L。然而，大多数诊断实验室使用免疫测定法来测量 PAC。使用免疫测定法的 SSST 截止值尚不清楚。我们假设在两种检测方法之间存在差异。
我们分析了最近一项研究中进行的 87 项 SSST 试验中的 80 项，该研究定义了 HPLC-MS/MS 截止值。通过阳性氟氢可的松抑制试验（FST）和/或肾上腺静脉采样的侧化在 65 项中确认了 PA，并在 15 项中通过阴性 FST 排除了 PA。使用 DiaSorin Liaison XL 分析仪在 SSST 样本中通过化学发光免疫测定法（PACIA）测量 PAC，进行接收者操作特征（ROC）分析以确定 PACIA 截止值。
ROC 显示，4 小时盐后 PACIA 对 PA 的诊断具有良好的性能（曲线下面积=0.893；P<.001），最佳诊断截止值为 171 pmol/L，灵敏度和特异性分别为 95.4%和 80.0%。更高的截止值 217 pmol/L 可提高特异性（86.7%），但敏感性较低（86.2%）。PACIA 测量值与 HPLC-MS 测量的 PAC 强烈相关（r=0.94，P<.001）。
当通过免疫测定法而不是 HPLC-MS/MS 测量 PAC 时，应采用更高的 SSST 诊断截止值。结果表明，如果 4 小时 PACIA 小于 171 pmol/L，则可排除 PA，如果 PACIA 大于化学发光免疫测定法的 217 pmol/L，则高度提示存在 PA。在 171 和 217 pmol/L 截止值之间存在灰色区域，可能反映了免疫测定法的特异性较低。
