title: Development and validation of a method using supported liquid extraction for aldosterone determination in human plasma by LC-MS/MS.
abstract: BACKGROUND
  Accurate quantitation of aldosterone is essential for screening, diagnosis and subtype classification in primary aldosteronism. A simple, sensitive method for aldosterone in human plasma using supported liquid extraction (SLE) in combination with liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed and validated.
  
  
  METHODS
  Plasma samples were diluted with water containing d7-aldosterone as internal standard. The samples were extracted with methyl-tert-butyl-ether (MTBE) on SLE cartridges. Separation was carried out on a Luna C18 (2) column using a methanol-water gradient. Detection was performed in the negative electrospray multiple reaction monitoring (MRM) quantitation. The use of water-based calibrators was evaluated against calibrators prepared in steroid-free serum.
  
  
  RESULTS
  The assay was linear up to 3265pmol/L with an LOQ of approximately 40pmol/L. Within-run and between-run precision for plasma aldosterone were less than 10% except at low level near LOQ but were still less than 14.7% (Westgard's desirable specification). The mean recovery of the analyte added to plasma was greater than 97.7% and matrix effects were less than 4%. Comparison with another LC-MS/MS method was performed on a more sensitive instrument (ABSciex TQ 5500) and gave the equation API 3000=0.957×TQ 5500+12.6, linear regression r(2)=0.974 (n=43). An estimation of the reference interval for adults was established on a group of healthy volunteers (n=53). Calibration with water-based calibrators was validated and can be used for measurement of aldosterone by LC-MS/MS.
  
  
  CONCLUSIONS
  This method is reliable, easy to perform on plasma specimens in a clinical environment and is attractive because of its simplicity.
authors.affiliation: Unit of Hormone and Nutrition, Department of Biochemistry, Toxicology and Pharmacology, University Hospital, Grenoble, France. Electronic address: CMeunier@chu-grenoble.fr.
authors.forename: Cécile
authors.initials: C
authors.lastname: Meunier
authors.affiliation: Unit of Hormone and Nutrition, Department of Biochemistry, Toxicology and Pharmacology, University Hospital, Grenoble, France. Electronic address: DBlondelle@chu-grenoble.fr.
authors.forename: Dominique
authors.initials: D
authors.lastname: Blondelle
authors.affiliation: Unit of Hormone and Nutrition, Department of Biochemistry, Toxicology and Pharmacology, University Hospital, Grenoble, France; HP2 Laboratory (INSERM U1042), The Joseph Fourier University, Grenoble, France. Electronic address: PFaure@chu-grenoble.fr.
authors.forename: Patrice
authors.initials: P
authors.lastname: Faure
authors.affiliation: Unit of Hypertension, Department of Cardiology, University Hospital, Grenoble, France; INSERM U1039, The Joseph Fourier University, Grenoble, France. Electronic address: jp.baguet@ghm-grenoble.fr.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Baguet
authors.affiliation: Department of Clinical Chemistry, University of Liège, CHU Sart-Tilman, Liège, Belgium. Electronic address: c.legoff@chu.ulg.ac.be.
authors.forename: Caroline
authors.initials: C
authors.lastname: Le Goff
authors.affiliation: Department of Endocrinology, University Hospital, Grenoble, France. Electronic address: OChabre@chu-grenoble.fr.
authors.forename: Olivier
authors.initials: O
authors.lastname: Chabre
authors.affiliation: Unit of Hormone and Nutrition, Department of Biochemistry, Toxicology and Pharmacology, University Hospital, Grenoble, France. Electronic address: VDucros@chu-grenoble.fr.
authors.forename: Véronique
authors.initials: V
authors.lastname: Ducros
mesh_terms: D000328:Adult; D000450:Aldosterone / Q000097:blood* / Q000302:isolation & purification*; D001774:Blood Chemical Analysis / Q000379:methods* / Q000592:standards; D002138:Calibration; D002648:Child; D002853:Chromatography, Liquid / Q000379:methods*; D005260:Female; D006801:Humans; D059625:Liquid-Liquid Extraction / Q000379:methods*; D008297:Male; D012016:Reference Values; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D000450:Aldosterone
keywords: Aldosterone; Hypertension; LC-MS/MS; SLE