Ammonia, Plasma

Diagnostic Use

Ammonia is a waste product produced by nitrogen (i.e. protein) metabolism. In normal health, ammonia is metabolised by the liver, forming the less toxic nitrogenous compound urea which is excreted renally.

Indications for testing
Diagnosis and monitoring of hepatic encephalopathy, investigation of suspected inborn errors of metabolism (e.g. urea cycle disorders), investigation of the patient with altered level of consciousness.

Department

Core Biochemistry

Delphic Registration Code

WAMM

Laboratory Handling

Phlebotomy

1 x EDTA (Lavender) No fist clenching. collect on ice, send to lab within 30 minutes. Haemolysed samples not suitable for analysis

Registration

Send on ice to separating

Separating

Spin 4000 RPM to yield platelet free plasma within 30 mins of collection. Store plasma frozen.

Synonyms

NH3

Turnaround Time

2 hours

Test Code

7214

Specimen Type

• Plasma

Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

4.0

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

0.6

Additional Specimen Information

Pre-Testing Requirements:
No fist clenching. collect on ice, send to lab within 30 minutes.
Paediatric Specimen - EDTA microtainer, 600 uL

Spin 4000 RPM to yield platelet free plasma within 30 mins of collection. Store plasma frozen.

Aliquot Instructions

Sample Type

• Plasma

Minimum Volume (ml)

0.5

Transport to Lab

Frozen
If overnight - Frozen

Additional Referral/Aliquot Information

Haemolysed samples not suitable for analysis

Interpretation

Hyperammonaemia presents clinically as encephalopathy. Patients may be confused or have a low GCS.

In adults, the most common cause of a high plasma ammonia is hepatic encephalopathy, usually due to cirrhosis or the presence of a portosystemic shunt.

Hyperammonaemia in babies/children may indicate an underlying inborn error of metabolism. Hyperammonaemia is a classic finding in urea cycle disorders, but can also occur in organic acidaemias and other rare metabolic disorders.

Other causes of hyperammonaemia include valproic acid toxicity, and infection with urease-containing bacteria (e.g. ureaplasma)

Reference Intervals

Aged <30 days:        <50umol/L

Aged >30 days:        11-32umol/L

Test Method

Performed on Beckman Coulter AU5822 analyser using Beckman Coulter reagents.

Non-Funded Test Cost

$70.63 (Exclusive of GST)

Billing Code

7214

Contact Information

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