title: Effect of low protein concentration on serum sodium measurement: pseudohypernatraemia and pseudonormonatraemia!
abstract: BACKGROUND
  The effect of high concentrations of protein or lipid on the measurement of plasma sodium by indirect ion selective electrode (ISE) causing pseudohyponatraemia and pseudonormonatraemia is well described. The effect of a low total protein concentration, however, has not been described.
  
  
  METHODS
  In order to examine this, over a 2-week period the total protein concentration was measured on all samples received for urea and electrolyte measurement. All samples with a low (<50 g/L) or a high (> 80 g/L) total protein concentration had sodium measured by both direct and indirect ISE.
  
  
  RESULTS
  There were approximately equal numbers of samples with a protein concentration less than 50 g/L (1.3%) as samples with a protein concentration greater than 80 g/L (1.3%). The frequency of erroneous sodium results owing to the use of an indirect ISE was less in hypoproteinaemic (2%) than in hyperproteinaemic (20%) samples.
authors.affiliation: Department of Clinical Chemistry, Nottingham City Hospital NHS Trust, UK.
authors.forename: T
authors.initials: T
authors.lastname: Lang
authors.forename: P
authors.initials: P
authors.lastname: Prinsloo
authors.forename: A F
authors.initials: AF
authors.lastname: Broughton
authors.forename: N
authors.initials: N
authors.lastname: Lawson
authors.forename: C B
authors.initials: CB
authors.lastname: Marenah
mesh_terms: D001798:Blood Proteins / Q000378:metabolism*; D006801:Humans; D006955:Hypernatremia / Q000378:metabolism*; D017736:Ion-Selective Electrodes; D012964:Sodium / Q000097:blood*
chemical_list: D001798:Blood Proteins; D012964:Sodium