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Direct urine ammonium measurement: time to discard urine anion and osmolar gaps

Direct urine ammonium measurement: time to discard urine anion and osmolar gaps BackgroundA 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.MethodsWe evaluated the adaptation of two widely available automated plasma ammonium assays for measurement of urinary ammonium.ResultsBoth 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.ConclusionsDirect 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. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Annals of Clinical Biochemistry: An International Journal of Biochemistry and Laboratory Medicine SAGE

Direct urine ammonium measurement: time to discard urine anion and osmolar gaps

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References (6)

Publisher
SAGE
Copyright
© 2012 The Association for Clinical Biochemistry
ISSN
0004-5632
eISSN
1758-1001
DOI
10.1258/acb.2012.012013
pmid
23038701
Publisher site
See Article on Publisher Site

Abstract

BackgroundA 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.MethodsWe evaluated the adaptation of two widely available automated plasma ammonium assays for measurement of urinary ammonium.ResultsBoth 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.ConclusionsDirect 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.

Journal

Annals of Clinical Biochemistry: An International Journal of Biochemistry and Laboratory Medicine – SAGE

Published: Nov 1, 2012

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