Ammonia, derived from the catabolism of amino acids and from the action of intestinal bacteria on dietary protein, is converted to urea in the liver hepatocytes and so rendered non-toxic. Studies have shown that excess ammonia can have a toxic effect on the central nervous system and clinical manifestations are typically neurological disturbances. Elevated levels of ammonia may be either due to "Inborn Errors of Metabolism", or secondary to other conditions.

Inborn errors of metabolism are the major cause of elevated ammonia in infants and usually the result of urea cycle enzyme deficiencies. Inherited disorders affecting the metabolism of the dibasic amino acids (lysine and ornithine) and those involving the metabolism of organic acids may also produce elevated levels of circulating ammonia. Elevated ammonia may also be observed in severe liver failure as may occur in Reye’s syndrome, viral hepatitis or cirrhosis.

This test cannot be added on to a previous specimen

Lavender (EDTA), 4mL

1. Following collection, mix sample by inverting 8 - 10 times to prevent clotting
2. Immediately place sample on ice

1. Spin and transfer plasma to a False bottom plasma/serum transport vial/tube (AHL), labelled as EDTA plasma, within 30 minutes of collection. If separation is delayed, the results may be falsely elevated.
2. If the specimen will not be tested within 1 hour of collection, the plasma must be frozen at <-20°C.

False bottom plasma/serum transport vial/tube (AHL)

Frozen (preferred) - 3 days

Refrigerated - 2 hours

Ambient - 30 minutes

• Hemolysis
  
  • Erythrocytes contain approximately 3 times more ammonia than does plasma
• Specimens should not be repeatedly frozen and thawed
• Specimens should be free of particulate matter and red blood cells
• Improper labels (unlabeled or mislabeled)
• Improper anticoagulant or ratio
• Delay in transport
• Improper storage temperature affecting results
• Inappropriate timing of collection
• Improper container
• Leaking container resulting in compromised specimen
• Quantity not sufficient (QNS)

Enzymatic

>110 µmol/L