title: Direct-measurement ion-selective electrodes: analytical error in hyponatremia.
abstract: Using two commercial direct ion-selective-electrode sodium and potassium analyzers, we found lower sodium values in cases of hyponatremia as compared with those by flame emission spectrophotometry or indirect ion-selective-electrode analyzers. It is shown that these errors can be eliminated by modifying the calibrant, and that there is a requirement for internationally agreed-upon reference standards for use by manufacturers and laboratory personnel to assess analytical performance of these analyzers.
mesh_terms: D001322:Autoanalysis; D004566:Electrodes; D006801:Humans; D007010:Hyponatremia / Q000097:blood*; D010783:Photometry / Q000379:methods; D012044:Regression Analysis; D012964:Sodium / Q000097:blood*
chemical_list: D012964:Sodium