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J Clin Pathol 65:457-462 doi:10.1136/jclinpath-2011-200564
  • Original article

Determination of serum aldosterone by liquid chromatography and tandem mass spectrometry: a liquid–liquid extraction method for the ABSCIEX API-5000 mass spectrometry system

  1. Daniel T Holmes1,3
  1. 1St. Paul's Hospital, Department of Pathology and Laboratory Medicine, Vancouver, British Columbia, Canada
  2. 2ABSCIEX, California, USA
  3. 3The University of British Columbia, Department of Pathology and Laboratory Medicine, Vancouver, British Columbia, Canada
  1. Correspondence to Dr Daniel T Holmes, Department of Pathology and Laboratory Medicine, St. Paul's Hospital, 1081 Burrard St, Vancouver, BC V5J 4B7, Canada; dtholmes{at}mail.ubc.ca

  1. Contributors GV finalised the chromatographic method, optimised the ionisation conditions and ran the method validation studies. CJ determined work on chromatographic conditions and identified some early problems with extraction method. JD established the initial LC-MS/MS method with onsite help from AW. H-FL established the initial ionisation conditions and provided critical technical advice. DH supervised the method development, performed all statistics, and prepared the manuscript, figures and tables.

  • Accepted 7 January 2012
  • Published Online First 12 March 2012

Abstract

Aims Accurate serum aldosterone determination is critical to the screening and diagnosis of primary aldosteronism, the localisation of aldosterone producing tumours, and the investigation of other disorders of the renin-angiotensin system. Mass spectrometry offers a means to overcome problems with method-dependent bias between competitive immunoassays for aldosterone. The authors have developed a simple, sensitive and precise liquid–liquid extraction aldosterone method for the ABSCIEX API-5000 liquid chromatography and tandem mass spectrometry (LC-MS/MS) system.

Methods Using d7-aldosterone internal standard, 500 μl of sample is extracted with 2500 μl of methyl tertbutyl ether followed by dry-down, reconstitution and LC-MS/MS analysis in ESI negative mode. Method validation was undertaken using standard approaches and comparison made against a commercial radioimmunoassay. Accuracy was assessed using EQA material with assigned aldosterone concentrations.

Results The assay was linear up to 3420 pmol/l (LOQ=50 pmol/l, LOD<22 pmol/l). Total CVs were ≤5% for concentrations ≥120 pmol/l and 10% at the LOQ. Mean accuracy was 98.5% against GCMS assigned material.

Conclusion The authors present a precise, sensitive and simple aldosterone method suitable for routine clinical use that requires no solid phase extraction or specialised ion sources.

Footnotes

  • Competing interests Hua-Fen Liu and Alex Wang are employed by ABSCIEX.

  • Ethics approval Approval provided by the University of British Columbia Research Ethics Board at St. Paul's Hospital.

  • Provenance and peer review Not commissioned; externally peer reviewed.