Laboratory Test Information Guide

Details for Ammonia,Plasma

Test Name: Ammonia,Plasma
Alternate Name(s):  
Laboratory: Core (VH)
Specimen Type: 4 mL K2 or K3EDTA Lavender top Vacutainer tube

0-2 years: 0.5 mL Lavender Microtainer (must be venous draw)
2-10 years: 3 mL Lavender top (must be venous draw).

NICU ONLY Micropick specimens are acceptable Use the CBC Microtainer tube, put on ice and deliver to Core Laboratory immediately.
Collection Information: Very unstable.

Specimens for ammonia must be received in the lab ON ICE within 30 minutes of being drawn.

Sample must be a venous draw.

Sample cannot be exposed to air.

Plasma may be sent from outside laboratories. Plasma must be sent FROZEN.
Test Schedule: As required
Turnaround time from when specimen
is received in testing laboratory:
3 hours
60 minutes
Reference Range: 
Male: 15-55 µmol/L
Female: 11-48 µmol/L
Effective Date: 2008-11-15
Revised Date: 2019-10-21
Critical Value: >149 μmo/L
Interpretive Comments: Therapeutic concentration of Cefoxitin, Acetaminophen (paracetamol), Ibuprofen, Sulfasalazine and Temozolomide interfere with the assay and lead to falsely result.

Elevated in Reye's syndrome, congenital urea cycle disorders and severe liver disease. Poor correlation with hepatic encephalopathy. Often used in the workup of neonatal coma.
Special Processing: SRA VH: Centrifuge immediately in cold and analyze ASAP.
SRA UH/SJ: Centrifuge immediately in cold, and keep aliquoted plasma at 4C. Send to VH within 2 hours during regular courier hours. After hours: STAT courier must be called.
Micropick specimens acceptable from NICU only. Centrifuge without delay in cold centrifuge if possible, aliquot and load on the correct Roche analyzer immediately after centrifugation
Comments: Hemolyzed samples are not acceptable as lysed red blood cells may elevate ammonia concentration.

Hemolysis interferes with result. Hemolyzed samples will have a comment attached to the result for children < 18. For adults ≥18, a comment will be attached to the result, unless hemolysis is >201, in which case the test will be canceled.

Lipemia may also cause interference.
Method of Analysis: Enzymatic Kinetic assay
Critical Information Required:  
Storage & Shipment: Centrifuge at 4C and transport aliquoted plasma on ice (minimize time of exposure to air).

Plasma may be stored at 4C for up to 3 hours in an air-tight container, if necessary.

Freeze for long term.
System Codes: 
Referred To:  

Questions? Comments? Contact Laura Gopaul