Prospective evaluation of aldosterone LC-MS/MS-specific cutoffs for the saline infusion test

Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) has become state of the art for the quantitative analysis of steroid hormones. Although method comparisons show that aldosterone measurement using LC-MS/MS yields considerably lower levels than immunoassays (IAs), method-specific cutoff values for primary aldosteronism (PA) are largely missing. Objective of this study was to analyze the diagnostic accuracy of proposed LC-MS/MS-specific cutoff values for the saline infusion test (SIT).From 2016 to 2019, 104 consecutive patients suspected of PA underwent the SIT and captopril challenge test in the tertiary medical center at the University Hospital of Leipzig, Germany. Patients with positive case confirmation underwent adrenal imaging and adrenal venous sampling for subtype classification.Overall, proposed assay-specific PACLC-MS/MS cutoff values for the SIT achieved higher diagnostic accuracy than established PACIA values with a sensitivity and specificity of 87.5% (95% CI: 71.0-96.5) and 97% (95% CI: 89.6-99.6) for a cutoff of 120 pmol/L and 93.8% (95% CI: 79.2-99.2) and 92.5% (95% CI: 83.4-97.5) for a cutoff of 94 pmol/L. The most accurate post-SIT PACLC-MS/MS cutoff value in this study was 83 pmol/L, yielding a sensitivity and specificity of 96.9% (95% CI: 83.8-99.9) and 92.5% (95% CI: 83.4-97.5), respectively.The present data confirm the need for the implication of lower method-specific aldosterone cutoff values for the diagnosis of PA with LC-MS/MS based aldosterone measurement.