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HelpTest Code NH3V Ammonia, Plasma
Useful For
Assisting in the diagnosis of hepatic coma
Investigating and monitoring treatment for inborn errors of metabolism
Evaluating patients with advanced liver disease
Reporting Name
Ammonia, PSpecimen Type
Plasma EDTAShipping Instructions
Plasma must be separated from cells and frozen within 2 hours of collection. Freeze plasma on dry ice or in a freezer (-60 to -80° C) for long-term storage or shipment.
Specimen Required
Collection Container/Tube: Lavender top (EDTA)
Submission Container/Tube: Plain, plastic screw-top tube
Specimen Volume: 0.5 mL or more
Collection Instructions:
1. Specimens should be put on ice immediately after collection.
2. Centrifuge at refrigerated temperature (4° C).
3. Aliquot plasma into plastic screw-top tube. Keep on ice.
4. Freeze plasma within 2 hours of collection.
Specimen Minimum Volume
See Specimen Collection
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma EDTA | Frozen (preferred) | 7 days | |
| Refrigerated | 2 hours |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Clinical Information
Ammonia is a waste product of protein catabolism; it is potentially toxic to the central nervous system. Increased plasma ammonia may be indicative of hepatic encephalopathy, hepatic coma in terminal stages of liver cirrhosis, hepatic failure, acute and subacute liver necrosis, and Reye's syndrome. Hyperammonemia may also be found with increasing dietary protein intake.
The major cause of hyperammonemia in infants includes inherited deficiencies of urea cycle enzymes, inherited metabolic disorders of organic acids and the dibasic amino acids lysine and ornithine, and severe liver disease.
Reference Values
≤30 mcmol/L
Interpretation
Plasma ammonia concentrations do not correlate well with the degree of hepatic encephalopathy.
Elevated ammonia concentration may also be found with increased dietary protein intake.
Plasma ammonia concentrations in newborns younger than one week are elevated compared to adults. Values less than or equal to 82 mcmol/L have been observed.(1)
Cautions
Specimens should be put on ice immediately after collection, centrifuged at refrigerated temperature, and plasma kept on ice until analyzed.
Proper specimen handling is critical; false increases in ammonia may occur if transport and processing instructions are not strictly followed.
Method Description
Patient specimen is deposited on the slide where the spreading layer promotes the uniform distribution of the specimen. Water and nonproteinaceous components travel to the underlying buffered reagent layer. The ammonia in the sample then diffuses through the semipermeable membrane to react with the ammonia indicator in the second reagent layer. The semipermeable membrane allows only the ammonia to pass and prevents buffer or hydroxyl ions from reaching the indicator layer where they would react with the indicator. After a fixed incubation period, the reflection density of the dye is measured using the white background of the spreading layer as a diffuse reflector.(Package insert: VITROS Chemistry Products Ammonia Instructions for Use, Version 11.0 Ortho-Clinical Diagnostics, Inc; 2019)
Day(s) Performed
Monday through Sunday
Report Available
Same day/1 dayPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
82140
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| NH3V | Ammonia, P | 16362-6 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| NH3V | Ammonia, P | 16362-6 |
Method Name
Photometric, Bromophenol Blue