Blood ammonia in dogs and cats using a point-of-care assay
Description
Point-of-care (POC) tests for blood ammonia (BA) are practical, but their use in veterinary species has not been well evaluated. This prospective study sought to establish an inferred reference interval for BA in dogs and cats using this method and to document conditions associated with hyperammonaemia in these species. Relevant clinical data, BA and diagnosis were recorded for all patients. Descriptive statistics, Pearson Chi2 and Mann-Whitney U testing was applied to assess for associations between clinical data and BA concentration. One-hundred seventy-five dogs and 63 cats were included, of which 124 (71%) dogs and 29 (46%) cats had undetectable ammonia. All dogs with BA >40µg/dL had liver disease. Only one dog without liver disease had BA >30µg/dL: a dog with hypoadrenocorticism and suspected gastrointestinal bleeding. All dogs with a clinical suspicion of hepatic encephalopathy and all dogs with hepatic vascular anomalies (congenital or acquired) had BA >40µg/dL. Following exclusion of cats with potential causes of hyperammonaemia, 9/19 cats had detectable ammonia (range 7-25µg/dL). All cats with a clinical suspicion of hepatic encephalopathy had BA >30µg/dL. This suggests that ammonia >30µg/dL and ammonia >25µg/dL may be clinically significant in dogs and cats respectively. Whilst dogs with ammonia >30µg/dL were likely to have liver disease, cats with ammonia >25µg/dL comprised a wide variety of disease pathologies.
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Steps to reproduce
The PochetChemTM BA (measurement range 0-400 µg/dL) was used for BA measurement in all patients. All patients had been starved for >8 hours prior to sampling. As per the manufacturer’s instructions, a single drop of surplus whole blood (20µL) was applied to the reagent strip immediately after collection for diagnostic purposes. Following application of the sample, the strip was left to rest on a flat surface for 180 seconds. The strip was then inserted into the reader, and the value registered on the screen was documented.