title: Enhancement of specificity of aldosterone measurement in human serum and plasma using 2D-LC-MS/MS and comparison with commercial immunoassays.
abstract: BACKGROUND
  Accurate measurement of aldosterone is important for the standardized testing of primary hyperaldosteronism. Commercial immunoassays show substantial between-method variations resulting in significant clinical consequences. We developed a specific two dimensional (2D)-LC-MS/MS method for measuring aldosterone in human serum and plasma and compared it with three commercial immunoassays and an LC-MS/MS method.
  
  
  METHODS
  250 μL samples, controls and calibrators spiked with d4-aldosterone were subjected to liquid-liquid extraction. The samples were analyzed using negative mode electrospray and 2D-LC followed by MS detection using an ABSciex 5500 mass spectrometer and compared with immunoassays of Siemens (Coat-A-Count), DiaSorin (CLIA-LIAISON), and IBL (ELISA). Data was acquired using multiple reaction-monitoring mode.
  
  
  RESULTS
  LOQ and LOD of the method were 0.04 and 0.02 nmol/L respectively. The assay was linear up to 166 nmol/L. Inter and intra-assay imprecision at 0.13, 1.38 and 8.30 nmol/L were <10%. Interferences were absent and no differences were observed between serum and plasma matrices. Method recovery ranged from 95% to 113%. Ion suppression was not observed. Evaluated immunoassays showed positive biases ranging between 22% and 37% when compared with the developed method.
  
  
  CONCLUSIONS
  We developed and validated an accurate method for measurement of aldosterone in human serum and plasma using 2D-LC-MS/MS which is suitable for clinical purposes. The method is faster than previously published LC-MS/MS methods, uses less sample, has adequate sensitivity while being able to preserve high specificity in a cost effective manner. Linearity of the assay makes it promising for urine and adrenal venous samples. Comparison with three commercial immunoassays demonstrates the advantages of the developed method.
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT 84108, United States. Electronic address: julie.ray@aruplab.com.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Ray
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT 84108, United States.
authors.forename: Mark M
authors.initials: MM
authors.lastname: Kushnir
authors.affiliation: Agilent Technologies Inc., Santa Clara, CA 95051, United States.
authors.forename: John
authors.initials: J
authors.lastname: Palmer
authors.affiliation: Phenomenex, Torrance, CA 90501, United States.
authors.forename: Seyed
authors.initials: S
authors.lastname: Sadjadi
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT 84108, United States; Department of Pathology, University of Utah, Salt Lake City, UT 84108, United States.
authors.forename: Alan L
authors.initials: AL
authors.lastname: Rockwood
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT 84108, United States; Department of Pathology, University of Utah, Salt Lake City, UT 84108, United States; Department of Medicine, University of Utah, Salt Lake City, UT 84108, United States.
authors.forename: A Wayne
authors.initials: AW
authors.lastname: Meikle
mesh_terms: D000450:Aldosterone / Q000097:blood* / Q000737:chemistry; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D016014:Linear Models; D059625:Liquid-Liquid Extraction; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000450:Aldosterone
keywords: 2D-LC–MS/MS; Aldosterone; Hypertension; Immunoassay; Liquid–liquid extraction; SLE