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Serum ammonia use: unnecessary, frequent and costly
  1. Elizabeth Aby1,
  2. Andrew P J Olson2,3,
  3. Nicholas Lim1
  1. 1 Division of Gastroenterology, Hepatology, and Nutrition, University of Minnesota, Minneapolis, Minnesota, USA
  2. 2 Department of Medicine, Division of General Internal Medicine, University of Minnesota, Minneapolis, Minnesota, USA
  3. 3 Department of Pediatrics, Division of Pediatric Hospital Medicine, University of Minnesota, Minneapolis, Minnesota, USA
  1. Correspondence to Dr Nicholas Lim, Division of Gastroenterology, Hepatology, and Nutrition, University of Minnesota System, Minneapolis, Minnesota, USA; nlim{at}


Background/objective While ammonia plays a role in the complex pathophysiology of hepatic encephalopathy (HE), serum ammonia is unreliable for both diagnosis of, and correlation with, neurological symptoms in patients with cirrhosis. We aimed to quantify ordering, cost and appropriate use of serum ammonia in a major Midwestern healthcare system.

Design/method Serum ammonia ordering in adult patients presenting to a large Midwestern health system was evaluated from 1 January 2015 to 31 December 2019.

Results Serum ammonia ordering was prevalent, with 20 338 tests ordered over 5 years. There were no differences in the number of inappropriate serum ammonia tests per 100 000 admissions for chronic liver disease over time (Pearson’s correlation coefficient=−0.24, p=0.70). As a proportion of total ammonia tests ordered, inappropriate tests increased over time (Pearson’s correlation coefficient=0.91, p=0.03). Inappropriate ordering was more common at community hospitals compared with the academic medical centre (99.3% vs 87.6%, p<0.001).

Conclusion Despite evidence that serum ammonia levels are unreliable for the diagnosis of HE and are not associated with severity of HE in individuals with cirrhosis, ordering remains prevalent, contributing to waste and potential harm.

  • hepatic encephalopathy
  • cirrhosis

Data availability statement

Data are available on reasonable request. Not applicable.

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Data availability statement

Data are available on reasonable request. Not applicable.

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  • Contributors Role in the Study: Study concept and design (EA and NL); acquisition of data (EA and NL); analysis and interpretation of data (EA and NL); drafting of the manuscript (EA, NL); critical revision of the manuscript for important intellectual content (EA, NL and APJO); statistical analysis (EA and NL); obtained funding (not applicable).

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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