Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

AAUCD
60202
Alpha-amino-n-butyric Acid (Abu)
Hydroxylysine (Hyl)
Proline (Pro)
Ornithine (Orn)
Cystathionine (Cth)
Cystine (Cys)
Lysine (Lys) 11-63 9-33 10-25 13-42
Methionine (Met)
Valine (Val) 14-61 9-28 8-20 11-40
Tyrosine (Tyr) 8-83 5-24 5-17
Homocystine (Hcy)
Isoleucine (Ile)
Leucine (Leu) 12-41 6-21 7-16 7-29
Phenylalanine (Phe) 7-40 5-18 7-21
Tryptophan (Trp)
Allo-isoleucine (AlloIle)
Clinical References: Rinaldo P, Hahn S, Matern D: Inborn errors of amino acid, organic acid, and
fatty acid metabolism. In Tietz Textbook of Clinical Chemistry and Molecular Diagnosis. Fourth edition.
Edited by CA Burtis, ER Ashwood, DE Bruns. St. Louis, WB Saunders Company, 2005, pp 2207-2247
Amino Acids, Urea Cycle Disorders Panel, Plasma
Clinical Information: Urea cycle disorders (UCD) are a group of inherited disorders of amino acid
catabolism that result when any of the enzymes in the urea cycle (carbamoylphosphate synthetase I
[CPS I]; ornithine transcarbamylase [OTC]; argininosuccinic acid synthetase [ASS]; argininosuccinic
acid lyase [ASL]; arginase [ARG]; or the cofactor producer, N-acetyl glutamate synthetase [NAGS]),
demonstrate deficient or reduced activity. The urea cycle serves to break down nitrogen and defects in
any of the steps of the pathway can result in an accumulation of ammonia, which can be toxic to the
nervous system. Infants with a complete enzyme deficiency typically appear normal at birth, but as
ammonia levels rise, may present with lethargy, seizures, hyper- or hypoventilation, and ultimately
coma or death. Individuals with partial enzyme deficiency may present later in life, typically following
an acute illness or other stressor. Symptoms may be less severe and may present with episodes of
psychosis, lethargy, cyclical vomiting, and behavioral abnormalities. All of the UCDs are inherited as
autosomal recessive disorders, with the exception of OTC deficiency, which is X-linked. UCDs may be
suspected with elevated ammonia, normal anion gap, and a normal glucose. Plasma amino acids can be
used to aid in the diagnosis of a UCD. Measurement of urinary orotic acid, enzyme activity (CPS I,
OTC, or NAGS), and molecular genetic testing can help to distinguish the conditions and allows for
diagnostic confirmation. Acute treatment for UCDs consists of dialysis and administration of nitrogen
scavenger drugs to reduce ammonia concentration. Chronic management typically involves restriction
of dietary protein with essential amino acid supplementation.
Useful For: Differential diagnosis and follow-up of patients with urea cycle disorders
Interpretation: The quantitative results of glutamine, ornithine, citrulline, arginine, and
argininosuccinic acid with age-dependent reference values are reported without added interpretation.
When applicable, reports of abnormal results may contain an interpretation based on available clinical
interpretation.
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