Ammonium - plasma

Last updated: Wednesday, 07, April, 2004

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Item Process
Specimen

5 mL blood in lithium heparin tube or 1 mL in paediatric tube, placed on ice. Plasma must be separated and assayed or frozen immediately.

Ammonium heparin tubes must not be used for collection.

Method

Spectrophotometry.

Reference Interval

<50 µmol/L (age related).

Application

Significant hyperammonemia during childhood can be observed with urea cycle defects, many of the organic acidemias, transient hyperammonemia of the newborn (THAN), and fatty acid oxidation defects.

Investigation of unexplained encephalopathy, especially if associated with vomiting.

Interpretation

Increased levels occur in genetic hyperammonaemias and are frequently seen in hepatic coma, especially with gastrointestinal bleeding. However, it is not a reliable or useful test for this condition.

Reference

Burton BK. Clin Liver Dis 2000; 4(4): 815-830.