• aldosterone
• LC-MS/MS

Introduction
Primary aldosteronism (PA) is a potentially curable disease that cause hypertension (HT). The first step in diagnosing PA consists in the determination of the aldosterone-renin-ratio (ARR). Recently, new methods with superior analytical performance for the measurement of both, aldosterone and renin, have been introduced in clinical practice. While aldosterone can be measured by liquid chromatography tandem mass spectrometry (LC-MS/MS) or automated immunoassays, renin is predominantly measured by direct immunoassays. ARR is strongly method dependent. Insufficient data exists on ARR in healthy subjects and PA patients when aldosterone and renin are measured with one of these new methods.
Aim of study
The present study evaluated the analytical performance a commercial LC-MS/MS method from Perkin Elmer (CHS ™ MSMS Steroids) for the measurement of aldosterone. In addition, we established a reference range for ARR when aldosterone is measured with the before mentioned LC-MS/MS method and renin is measured by a direct immunoassay from DiaSorin on a Liaison XL auto-analyser.
Materials and methods
The Perkin Elmer CHS ™ MSMS Steroids method is a multiplex assays. Analyses were performed on a Shimadzu 8050 LC-MS/MS. The analytical performance of aldosterone measurement was evaluated determining the following performance indices: LoD, LoQ, recovery, carryover, linearity and precision. For the establishment of the ARR reference range serum aldosterone and plasma renin were measured in samples from 128 normotensive blood donors.
Results
LOD and LOQ were respectively 12.9 pg/mL and 26 pg/mL. Intraassay precision at different concentrations was 7% ( at 79.9 pg/mL.), 7.6% ( at 161.8 pg/mL.) and 1.5% ( at 3506.08 pg/mL). Interassay precision was 8.5%, 9.6% e 5.1% respectively. Recovery ranged between 80.5 and 104.4%. Between x and y the method was linear. ARR in healthy blood donors varied between 0.6-62.4 pg/µU with a median of 5.7 pg/µU. The 2.5th and 97.5th percentiles (without outlier) were 1.0 and 16.4, respectively.
Conclusion
The performance characteristics of the here tested LC-MS/MS method for the measurement of aldosterone are satisfactory and justify the use of this test in clinical practice.