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Test Code NH4 AMMONIA

Important Note

1.    Collect blood from a stasis-free vein of fasting patient.
2.    Smoking should be avoided prior to collection.
3.    Immediately after drawing patient, place specimen on ICE.

Specimen and Container/Tube

Specimen Type: Plasma

Preferred Specimen: Lavendar + Ice

Specimen Stability

Storage Temperature

Stability

Room temperature

60 minutes

Refrigerated

2 hours

Frozen (-15 to -25oC)

3 days

Frozen (-60 to -90oC)

4 weeks

 

Note: Specimen must be separated from cells

Collection Instructions

Collect specimen per standard laboratory collection procedures. 

 

Specimen Handling and Transport Instructions

UCMC Onsite Instructions: 

Collect specimen per standard collection procedure and send to laboratory immediately. 

 

UCMC Offsite and UC MedLab Outreach Instructions: 

  • Samples should be centrifuged within 2 hours of collection.
  • Centrifuge specimens at >2500 x g for 10 minutes at 2-8oC.
  • Aliquot sample into plastic transport tube containing a minimum of 0.2 mL of specimen.
  • Samples must be sent frozen.

Rejection Criteria

  • Common specimen rejected situations include: incorrect specimen type, insufficient volume, missing or incomplete specimen identifiers, incorrect specimen transport, or specimens outside stability limits. 
  • Specimens that are clotted or grossly hemolyzed.
  • Specimens that were transported unspun/whole blood and draw time is greater than 6 hours.

Reference Values

 

Test

Age

Sex

Reference Range

NH4

All

All

12-41 μmol/L

Note: Reference range based on in-house studies, recommendations from Tietz Textbook of Clinical Chemistry, and Roche product literature.  

Critical Values

Analyte

Unit

Low

High

Age

N/A

N/A

N/A

N/A

N/A

Turnaround Time

Turnaround times are relative to the time the specimen is received in the test laboratory. 

 

STAT Turnaround Time: 1 hour

Routine Turnaround Time: 4 hours

Testing Schedule: 24/7

Clinical Indications

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.

Test Components

Ammonia

CPT Codes

82140

LOINC Codes

16362-6

Methodology

Immunoturbidimetric Assay (Roche Diagnostics)

Synonyms/Keyword Search

NH4

Ammonia

Additional Information

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.

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.

Last Review Date

07/02/2024

Volume

Preferred Volume: 0.5 mL

Minimum Volume: 0.2 mL