Newcastle Laboratories

Ammonia, plasma

Clinical Background:

Measurement of ammonia should be a first line biochemical investigationin the acutely ill neonate/infant and also in cases of unexplained altered mental state or prolonged vomiting without diarrhoe...

Measurement of ammonia should be a first line biochemical investigationin the acutely ill neonate/infant and also in cases of unexplained altered mental state or prolonged vomiting without diarrhoea in patients of any age.

Hyperammonaemia results from defective catabolism of amino acids to urea. Ammonia is neurotoxic and symptoms of hyperammonaemia are essentially neurological but with varying severity and age of onset.

The following guidelines are available:

  • British Inherited Metabolic Diseases Group (BIMDG) Emergency guideline for management of undiagnosed hyperammonaemia

http://www.bimdg.org.uk/site/guidelines.asp

  • UK Metabolic Biochemistry Network (MetBioNet) guideline on investigation of hyperammonaemia

http://www.metbio.net/metbioGuidelines.asp

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Test Details

  • Discipline:

    Biochemistry

    Biochemistry

  • Specimen Container Adult:

    EDTA plasma

    EDTA plasma

  • Specimen Container Paediatric:

    EDTA plasma

    EDTA plasma

  • Minimum Volume Adult:

    1 mL blood

    1 mL blood

  • Minimum Volume Paediatric:

    0.5 mL blood

    0.5 mL blood

  • Special Requirement:

    The laboratory will analyse all samples received. However to minimise falsely high results samples should be placed on ice following collection and brought immediately to the laboratory.

    Please con...

    The laboratory will analyse all samples received. However to minimise falsely high results samples should be placed on ice following collection and brought immediately to the laboratory.

    Please contact the laboratory to inform that sample is being sent.

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  • Sample Stability:

    Falsely high results may be obtained if samples are kept unseparated at ambient temperature.

    Falsely high results may be obtained if samples are kept unseparated at ambient temperature.

  • Transport Requirements:

    Bring immediately to laboratory, marked for urgent analysis. Transport on ice is strongly recommended, although if ice not available laboratory will still perform analysis.

    Bring immediately to laboratory, marked for urgent analysis. Transport on ice is strongly recommended, although if ice not available laboratory will still perform analysis.

  • Interpretation:

    Ammonia > 200 µmol/L in neonates or > 150 µmol/L in older patients requires immediate attention. Consider contacting a Metabolic specialist.

     

    Causes of hyperammonaemia can be split into:

    Inherited...

    Ammonia > 200 µmol/L in neonates or > 150 µmol/L in older patients requires immediate attention. Consider contacting a Metabolic specialist.

     

    Causes of hyperammonaemia can be split into:

    Inherited metabolic disorders: including urea cycle defects, other amino acid disorders, organic acidurias, fatty acid oxidation defects
    Acquired causes: including liver dysfunction and certain medications
    Artefactual/other: including sample haemolysis, delayed analysis, transient hyperammonaemia of newborn.


    First line investigations into hyperammonaemia requires:

    Repeat plasma ammonia
    Blood gases
    U&E
    LFT
    Clotting screen
    Plasma glucose
    Plasma lactate
    Serum/plasma calcium
    Blood cultures
    Urine ketones

     

    If an inherited metabolic cause is suspected then the following tests should be requested, before initiation of treatment if at all possible:

    Urine organic acids
    Urine and plasma amino acids
    Urine orotic acid
    Blood spot acylcarnitines

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  • Reference Ranges:

    0 - 4 week: 0 - 100 µmol/L
    4 weeks and older: 0 - 50 µmol/L

    0 - 4 week: 0 - 100 µmol/L
    4 weeks and older: 0 - 50 µmol/L

  • Routine Contact Name:

    Duty Biochemist

  • Routine Telephone:

    Freeman: 0191 244 8889
    RVI: 0191 282 9719

    Freeman: 0191 244 8889
    RVI: 0191 282 9719

  • Routine Email:

    - For external users: TNU-Tr.duty.biochemist@nhs.net

    - For Trust users: DutyBiochemist@nuth.nhs.uk

Availability:

All times
All sites

Turn Around:

Within 1 hour

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