Ammonia, Plasma

CPT Code(s):

82140

Collection Procedure:

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.
  • Patient should not clench fist.
  • Transfer specimen to a plastic transport tube before freezing.
  • Date and time specimen was drawn must be written on tube of blood and request form.

Specimen Requirements:

Type: Plasma

Container/Tube: Lavender-top (EDTA) tube

Sample Volume: 1 mL

Storage:

  • Collect on ice, separate plasma from cells and freeze immediately
  • Sample is stable 14 days froozen

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.

Ammonia measurements are mainly of use in the diagnosis of urea cycle deficiencies (any neonate with unexplained nausea, vomiting, or neurological deterioration appearing after first feeding), and they play an important part in the detection of Reye syndrome.

Methodology:

Enzymatic

Reference Values:

Male: 27−102 μg/dL
Female: 19−87 μg/dL