Laboratory: Clinical Biochemistry
Test Name:
AMMONIA - (P)
Test Code: AMM
Clinical Information:
Normal values are for venous samples.  Arterial values are slightly lower than venous.  Capillary values are higher.

Test Indications:
The major source of circulating ammonia is the GI tract. Under normal conditions, ammonia is metabolized to urea by liver enzymes. Several diseases, both inherited and acquired, cause elevated ammonia (hyperammonemia). Inherited deficiencies of the urea cycle enzymes are the major cause of hyperammonemia in infants. The acquired hyperammonemia diseases are caused by liver disease, renal failure and Reyes Syndrome. Elevated ammonia is toxic to the central nervous system.

Patient Preparation Instructions:
Patients must not smoke prior to specimen collection.
Collection Devices:
Collect ON ICE and transport to Lab immediately.
Specimen Required:

Collected on ice. Stability 3 hours refrigerated, 1 day frozen

Collect full tube(s) of blood to applicable fill line.
Referral:

Plasma:  2.0 mL              
Pediatric Plasma:  0.3 mL (applies to microtainer collection).
Send frozen plasma which must remain frozen until received at Laboratory.

Samples must be transferred to an aliquot tube and stored frozen within 30 minutes of collection. Ship on dry ice if transportation is required. See #110-10-05 Serum / Plasma Separation & Transport for shipping instructions.
Requisition:
Reference Values:
< 1 d: 64 - 107 μmol/L           
1 d - 2 wk: 56 - 92 
3 wk - 17 y: 21 - 50
≥ 18 y: 11 - 35
(μmol/L x 1.8 = μg/dL)
Availability:
Stat or Routine
See Also:
More Information:
Centrifuge specimen immediately upon arrival in Laboratory. Analyze without delay (ideally within 20 minutes). In the event that analysis cannot be completed, freeze the plasma within 20 minutes of sample collection. Clotting releases large amounts of ammonia so specimens containing clots are unsuitable and must be rejected. Capillary blood: Values are higher than venous plasma so this is not recommended. If capillary collection is necessary: the capillary site should be warmed to produce a good blood flow and cleansed well to ensure no trace of sweat remains. Sample should be collected into 1 microtainer tube (mix well with each drop), placed on ice and sent to the lab immediately.