title: Sodium interference in the determination of urinary aldosterone.
abstract: OBJECTIVE
  Primary hyperaldosteronism (PHA) is one of the most common endocrine forms of secondary hypertension. Among the most used confirmatory tests for PHA is urinary aldosterone determination after oral sodium loading test. The primary aim of our study was to investigate if sodium concentrations interfere with urinary aldosterone in an automated competitive immunoassay (Liaison®) as well as to verify the manufacturer's specifications.
  
  
  METHODS
  24-hr urine samples were collected and stored frozen until assayed. Two pools at low and high aldosterone concentrations were prepared. Verification of performance for precision was tested according to Clinical and Laboratory Standards Institute (CLSI) document EP15-A2 and interference with increasing concentrations of NaCl according to CLSI EP7-A2.
  
  
  RESULTS
  The assay met the quality specifications according to optimal biological variation. Our results show that sodium concentrations up to 200mmol/L do not interfere on urinary aldosterone quantification, but sodium concentrations above 486mmol/L negatively interfere with the test.
  
  
  CONCLUSIONS
  The Liaison® automated method is useful for aldosterone determination in the PHA confirmatory test, but interferences with NaCl may occur. It is therefore recommended to determine urinary NaCl before measuring urinary aldosterone to avoid falsely low results.
authors.affiliation: Department of Clinical Biochemistry, Hospital Germans Trias i Pujol, Autonomous University of Barcelona, Badalona, Spain. Electronic address: martaaldea5@gmail.com.
authors.forename: Marta Lucía
authors.initials: ML
authors.lastname: Aldea
authors.affiliation: Department of Clinical Biochemistry, Hospital Germans Trias i Pujol, Autonomous University of Barcelona, Badalona, Spain.
authors.forename: Jaume
authors.initials: J
authors.lastname: Barallat
authors.affiliation: Department of Clinical Biochemistry, Hospital Germans Trias i Pujol, Autonomous University of Barcelona, Badalona, Spain.
authors.forename: María Amparo
authors.initials: MA
authors.lastname: Martín
authors.affiliation: Department of Clinical Biochemistry, Hospital Germans Trias i Pujol, Autonomous University of Barcelona, Badalona, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: Rosas
authors.affiliation: Department of Clinical Biochemistry, Hospital Germans Trias i Pujol, Autonomous University of Barcelona, Badalona, Spain.
authors.forename: María Cruz
authors.initials: MC
authors.lastname: Pastor
authors.affiliation: Department of Clinical Biochemistry, Hospital Germans Trias i Pujol, Autonomous University of Barcelona, Badalona, Spain.
authors.forename: María Luisa
authors.initials: ML
authors.lastname: Granada
mesh_terms: D000450:Aldosterone / Q000737:chemistry / Q000652:urine*; D006801:Humans; D006929:Hyperaldosteronism / Q000652:urine; D006973:Hypertension; D007118:Immunoassay / Q000379:methods*; D015203:Reproducibility of Results; D012964:Sodium / Q000737:chemistry / Q000652:urine*; D012965:Sodium Chloride / Q000378:metabolism
chemical_list: D012965:Sodium Chloride; D000450:Aldosterone; D012964:Sodium
keywords: Aldosterone; Immunoassay; Liaison® analyzer; Primary hyperaldosteronism; Sodium interference