How useful are ammonia levels in diagnosing hepatic encephalopathy?

Bottom line:  In patients with cirrhosis presenting with altered mental status, clinical evaluation remains the gold standard for diagnosis.
Summary: DynaMed states that ammonia levels are not established as a diagnostic test for HE- cites review articles and ACG guidelines.
Ong JP, et al.  Correlation between ammonia levels and the severity of hepatic encephalopathy.  Am J Med. 2003 Feb 15;114(3):188-93.   One small prospective study (N=121) of consecutive patients diagnosed with cirrhosis (confirmed by biopsy or signs of portal hypertension.) Mental status diagnosed by single investigator using West Haven Criteria.  Ammonia levels were measured after mental status assessment.  Figure on pp. 190-191 includes box plots that compare the venous and arterial total and partial ammonia among patients by severity of encephalopathy.

Repost of July 14, 2010

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About Amy

Clinical Informationist at EUH Branch Library
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