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Comparative accuracy and precision of two commercial laboratory analyzers for the quantification of ammonia in
Nausikaa Devriendt1, Matan Or1, Evelyne Meyer2
1Small Animal Department, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
Background:
Hyperammonemia is one of the contributing factors of hepatic encephalopathy (HE). Although blood ammonia concentrations are frequently measured in patients suspected of HE, systemic levels do not necessarily reflect the amount of ammonia in the central nervous system. Measuring ammonia in cerebrospinal fluid (CSF) can help to understand HE better and potentially improve the diagnosis and follow-up of patients with HE.
Objectives:
The objectives of this technical report were to evaluate the accuracy and precision of two commercial blood ammonia analyzers (Catalyst Dx, CatDX and Pocket Chem BA, PocBA) to measure CSF ammonia concentrations.
Methods:
A pool of normal equine CSF was spiked with concentrated ammonia, and a series of six spiked samples were measured in parallel with both CatDx and PocBA.
Results:
CatDx and PocBA data correlated excellently with but differed significantly from the spiked ammonia concentrations. These differences were smaller when ammonia CSF concentrations were measured with the PocBA than with the CatDx. In addition, values obtained with the PocBA were more precise than those measured with the CatDx, especially for low ammonia concentrations.
Conclusion:
This in-house comparative study shows that ammonia concentrations in spiked equine CSF correlate well with those measured by two commercial blood ammonia analyzers. Nevertheless, concentrations obtained with the PocBA are more accurate and more precise than those obtained with the CatDx, making the former device the preferred choice for clinical veterinary applications.
