An automated Immunoaffinity liquid chromatography-tandem mass spectrometry assay for quantification of aldosterone in human plasma.

The diagnosis of primary aldosteronism (PA) relies on the accurate determination of aldosterone. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has long been considered the gold standard for aldosterone quantification but it is hindered by labor-intensive sample preparation. To address this, we developed an immunoaffinity-mass spectrometry (iMS) assay on a fully automated device combining anti-aldosterone antibodies with stable isotope-labeled internal standards (IS). This method completes sample preparation within 15 min for at least six parallel samples in parallel with minimal manual intervention. The key performance metrics include a lower limit of quantitation (LOQ) of 50 pg/mL, recovery rates between 105.1 and 113.9 %, and linearity in the range of 50-2000 pg/mL (R2 = 0.9993). Inter-assay coefficient of variation (CV) ranged from 2.33 % to 3.91 %. In addition, plasma aldosterone concentrations by iMS and immunoassay had a high correlation coefficient (R = 0.947). Overall, this automated high-throughput platform delivers clinical-grade sensitivity, precision, and scalability, making it suitable for routine testing and adaptable for other clinical analytes.