期刊
CLINICAL BIOCHEMISTRY
卷 50, 期 9, 页码 537-539出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.clinbiochem.2017.01.002
关键词
Ammonia; Plasma; Hyperammonemia
An assessment of blood ammonia concentration is common medical practice in the evaluation of an individual with an unexplained mental status change or coma. The determination of a blood ammonia level is most commonly done using a glutamate dehydrogenase (GLDH)-based assay, although there are many potential sources of artifact and the literature is inconsistent regarding key preanalytic issues. Using a GLDH-based assay, we first investigated matrix effects using three anticoagulants: heparin, EDTA and oxalate. Heparin-anticoagulated plasma was substantially less precise than EDTA-and oxalate-anticoagulated plasma. Oxalate-anticoagulated plasma showed a greater baseline of apparent ammonia than either heparin-or EDTA-derived plasma, presumably due to interferants. We then evaluated the stability of EDTA-anticoagulated plasma for assessment of ammonia when stored at 4 degrees C,-14 degrees C or -70 degrees C. There was a linear increase of ammonia with storage at both 4 degrees C and -14 degrees C. Plasma kept at -70 degrees C for up to three weeks showed no change in measured ammonia relative to the baseline determination. This work clarifies preanalytic conditions for which a precise determination of ammonia can be accomplished using a GLDH-based assay. (C) 2017 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.
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