AMMONIUM - plasma

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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: <70 µmol/L.

Application: Investigation of unexplained encephalopathy, esp if associated with vomiting.

Interpretation: Increased levels occur in genetic hyperammonaemias and Reye syndrome. Increased levels are frequently seen in hepatic coma, esp with gastrointestinal bleeding, but it is not a reliable or useful test for this condition.

Reference: Colombo JP et al. Clin Chim Acta 1984; 138: 283-291.

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