BACKGROUND: A failure of urine ammonium to increase during acidosis indicates impaired renal acidification, and the urinary ammonium concentration is therefore a useful investigation in determining the cause of a metabolic acidosis. However, urine ammonium measurements are not widely available in routine diagnostic laboratories. This has led to the use of urine anion or osmolar gaps, which are unsatisfactory as surrogates for urine ammonium measurement. METHODS: We evaluated the adaptation of two widely available automated plasma ammonium assays for measurement of urinary ammonium. RESULTS: Both assays showed good recovery and linearity in urine samples spiked with ammonium chloride, and acceptable precision. Urine ammonium concentrations estimated from urinary anion and osmolar gaps showed poor agreement with measured urine ammonium concentrations. CONCLUSIONS: Direct urine ammonium measurements are easily performed with modern autoanalysers by simple adaptation of routine plasma ammonium assays. The use of urine anion and osmolar gaps should be abandoned where direct measurement is available.
BACKGROUND: A failure of urine ammonium to increase during acidosis indicates impaired renal acidification, and the urinary ammonium concentration is therefore a useful investigation in determining the cause of a metabolic acidosis. However, urine ammonium measurements are not widely available in routine diagnostic laboratories. This has led to the use of urine anion or osmolar gaps, which are unsatisfactory as surrogates for urine ammonium measurement. METHODS: We evaluated the adaptation of two widely available automated plasma ammonium assays for measurement of urinary ammonium. RESULTS: Both assays showed good recovery and linearity in urine samples spiked with ammonium chloride, and acceptable precision. Urine ammonium concentrations estimated from urinary anion and osmolar gaps showed poor agreement with measured urine ammonium concentrations. CONCLUSIONS: Direct urine ammonium measurements are easily performed with modern autoanalysers by simple adaptation of routine plasma ammonium assays. The use of urine anion and osmolar gaps should be abandoned where direct measurement is available.
Authors: Richard Brunner; Andreas Drolz; Thomas-Matthias Scherzer; Katharina Staufer; Valentin Fuhrmann; Christian Zauner; Ulrike Holzinger; Bruno Schneeweiß Journal: Crit Care Date: 2015-04-06 Impact factor: 9.097
Authors: James C Williams; Giovanni Gambaro; Allen Rodgers; John Asplin; Olivier Bonny; Antonia Costa-Bauzá; Pietro Manuel Ferraro; Giovanni Fogazzi; Daniel G Fuster; David S Goldfarb; Félix Grases; Ita P Heilberg; Dik Kok; Emmanuel Letavernier; Giuseppe Lippi; Martino Marangella; Antonio Nouvenne; Michele Petrarulo; Roswitha Siener; Hans-Göran Tiselius; Olivier Traxer; Alberto Trinchieri; Emanuele Croppi; William G Robertson Journal: Urolithiasis Date: 2020-10-13 Impact factor: 3.436