Ammonia, Plasma

Clinical Use

Use

Ammonia is elevated in the following conditions: liver disease, urinary tract infection with distention and stasis, Reye syndrome, inborn errors of metabolism including deficiency of enzymes in the urea cycle, HHH syndrome (hyperammonemia-homocitrullinuria, hyperornithinemia), some normal neonates (usually returning to normal in 48 hours), total parenteral nutrition, ureterosigmoidostomy, and sodium valproate therapy. Ammonia determination is indicated in neonates with neurological deterioration, subjects with lethargy and/or emesis not explained, and in patients with possible encephalopathy.

Special Instructions

Not provided.

Limitations

There is a poor correlation between blood ammonia levels and hepatic coma. Ammonia determinations are not reliable predictors of impending hepatic coma and are not always elevated in all patients with urea cycle disorders. High protein diets and gastrointestinal hemorrhage can affect ammonia levels. Conditions like cirrhosis may alter hepatic blood flow, leading to elevated levels.

Test Details

Methodology

Automated Analyzer (Clinical Chemistry)

Biomarkers

Ammonia

Analyte

Ammonia Level

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

LOINC Codes

Order Codes

22763-7 - Ammonia Plas-mCnc

Result Codes

22763-7 - Ammonia Plas-mCnc

Result Turnaround Time

1-2 days

Specimen

Plasma

Volume

1 mL

Minimum Volume

0.5 mL

Container

Lavender-top (EDTA) tube; EDTA is the only acceptable anticoagulant.

Collection Instructions

Tube must be filled completely and kept tightly stoppered at all times. Mix well. Specimen must be placed on ice immediately. Separate plasma from cells within 15 minutes of collection. Transfer specimen to a plastic transport tube before freezing. Avoid contamination of samples by ammonia.

Patient Preparation

Patient should be fasting 12 to 14 hours to avoid lipemia, which interferes with the test.

Storage Instructions

Freeze. Ammonia is stable for several days at -20°C. Caution: Blood ammonia increases rapidly at room temperature.

Causes for Rejection

Hemolysis, specimen not received frozen, certain anticoagulants like citrate, oxalate, ammonium heparin, or sodium fluoride, lithium heparin, serum specimen, lipemia