Ammonia Testing in Cirrhosis

Key Guideline Recommendations on Ammonia Testing

The Korean Association for the Study of the Liver recommends that there are various methods of measuring ammonia concentrations, such as those involving the venous or arterial blood or plasma, and emphasizes that the normal range varies depending on the specific measurement method, a suitable reference value should be used 1, 2
The diagnosis of hepatic encephalopathy should be made based on clinical symptoms, not ammonia levels alone, as stated by the Clinical and Molecular Hepatology 1, 2

A normal ammonia level has high negative predictive value for hepatic encephalopathy and should immediately trigger investigation for alternative causes of altered mental status, according to the European Association for the Study of the Liver 3, 4, 5
The European Association for the Study of the Liver recommends measuring ammonia once at presentation in patients with delirium and liver disease to exclude hepatic encephalopathy 4

The American Association for the Study of Liver Diseases states that improper collection technique leads to falsely elevated results and renders the test useless, and essential steps include collecting from fasting patients, avoiding venous stasis, using EDTA or lithium heparin tubes, placing immediately on ice, processing within 15 minutes, and analyzing immediately 4

The Clinical and Molecular Hepatology recommends that in a cirrhotic patient with altered mental status, measure ammonia once at presentation, and if ammonia is normal, hepatic encephalopathy is effectively ruled out, and immediately investigate alternative causes 1, 2, 3, 4, 5
If ammonia is elevated, diagnose hepatic encephalopathy based on clinical symptoms and exclusion of other causes, identify and treat precipitating factors, and initiate lactulose or rifaximin therapy 1, 2, 3

The Korean Association for the Study of the Liver recommends that the diagnosis of hepatic encephalopathy requires clinical symptoms and exclusion of other causes, and do not assume hepatic encephalopathy based on elevated ammonia alone 1, 2, 4
The European Association for the Study of the Liver recommends that do not delay brain imaging in first episodes or atypical presentations, and do not use ammonia trending to guide therapy 3, 4
The American Association for the Study of Liver Diseases states that do not overlook proper collection technique, and do not ignore normal ammonia in suspected hepatic encephalopathy 3, 4, 5