Stabilizing specimens for routine ammonia testing in the clinical laboratory.

Autor: Gifford JL; Calgary Laboratory Services, Calgary, AB, Canada; Department of Pathology and Laboratory Medicine, Faculty of Medicine, University of Calgary, AB, Canada., Nguyen WNT; Calgary Laboratory Services, Calgary, AB, Canada., de Koning L; Calgary Laboratory Services, Calgary, AB, Canada; Department of Pathology and Laboratory Medicine, Faculty of Medicine, University of Calgary, AB, Canada., Seiden-Long I; Calgary Laboratory Services, Calgary, AB, Canada; Department of Pathology and Laboratory Medicine, Faculty of Medicine, University of Calgary, AB, Canada. Electronic address: Isolde.seidenlong@cls.ab.ca.
Jazyk: angličtina
Zdroj: Clinica chimica acta; international journal of clinical chemistry [Clin Chim Acta] 2018 Mar; Vol. 478, pp. 37-43. Date of Electronic Publication: 2017 Dec 16.
DOI: 10.1016/j.cca.2017.12.022
Abstrakt: Background: In vitro deamination generates ammonia in freshly collected blood specimens. To prevent this, samples for ammonia testing are usually collected on ice and run rapidly (e.g., within 1h). We developed a method to stabilize specimens for ammonia analysis.
Methods: Following plasma separation, 500μmol/l cycloserine or a combination of 2mmol/l sodium borate with 5mmol/l l-serine were added to sample pools with normal or increased concentrations of ALT and/or GGT to inhibit deamination; and/or residual platelets were removed via centrifugation. Sample pools were then incubated at room temperature or 4°C. Untreated sample pools were also incubated at -80°C. Ammonia was measured at 0, 1, 2, 4, 8, 16, and 24h.
Results: When incubated at 4°C without treatment, sample pools with enzymes within their reference limit had an increase of 0.5μmol/l/h, whereas sample pools with ALT and/or GGT activity above their upper reference limit had an increase of 3.6μmol/l/h (p<0.001). When sample pools were incubated at 4°C with sodium borate/l-serine, the rate of ammonia increase was significantly reduced in samples with normal (0.3μmol/l/h, p<0.001 vs. untreated controls) or high enzyme activity (0.1μmol/l/h, p<0.001 vs. untreated controls). Independent of the ALT and/or GGT concentrations, storing the sample at -80°C also preserved the specimens for ammonia analysis (0.2μmol/l/h, p<0.001 vs. untreated controls).
Conclusions: By combining sodium borate/l-serine with refrigeration, plasma ammonia specimens can be stabilized for >12h.
(Copyright © 2017 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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