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

GGT
8677
common in those of eastern European descent and accounts for 25% to 40% of the alleles in this
population. The L195P mutation is observed in 5% to 7% of classic galactosemia. The Duarte variant
(N314D) is found in 5% of the general United States population. The above mutations, plus the LA
variant, are included in GCT/84360 Galactosemia Reflex, Blood, which is the preferred test for the
diagnosis of galactosemia or for follow-up to positive newborn screening results. These mutations are
also included in GAL6/84366 Galactosemia Gene Analysis (6-Mutation Panel). Full sequencing of the
GALT gene can be useful for the identification of mutations when 1 or no mutations are found with
these tests in an individual with demonstrated GALT activity deficiency. Full sequencing of the GALT
gene identifies over 95% of the sequence variants in the coding region and splice junctions. See
Galactosemia Testing Algorithm in Special Instructions for additional information. Refer to
Galactosemia: Current Testing Strategy and Aids for Test Selection, Mayo Medical Laboratories
Communique 2005 May;30(5) for more information regarding diagnostic strategy.
Useful For: Identifying mutations in individuals who test negative for the common mutations and who
have a biochemical diagnosis of galactosemia or galactose-1-phosphate uridyltransferase activity levels
indicative of carrier status
Interpretation: All detected alterations will be evaluated according to the American College of
Medical Genetics and Genomics (AMCG) recommendations. Variants will be classified based on known,
predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or
known significance.
Reference Values:
An interpretive report will be provided.
Clinical References: 1. Elsas LJ 2nd, Lai K: The molecular biology of galactosemia. Genet Med
1998 Nov-Dec;1(1):40-48 2. Novelli G, Reichardt JK: Molecular basis of disorders of human galactose
metabolism: past, present, and future. Mol Genet Metab 2000 Sep-Oct;71(1-2):62-65 3. Bosch AM, Ijlst
L, Oostheim W, et al: Identification of novel mutations in classical galactosemia. Hum Mutat 2005
May;25(5):502 4. Richards CS, Bale S, Bellissimo DB, et al: ACMG recommendations for standards for
interpretation and reporting of sequence variations: Revisions 2007. Genet Med 2008;10(4):294-300
Gamma-Glutamyltransferase (GGT), Serum
Clinical Information: Gamma-glutamyltransferase (GGT) is primarily present in kidney, liver, and
pancreatic cells. Small amounts are present in other tissues. Even though renal tissue has the highest level
of GGT, the enzyme present in the serum appears to originate primarily from the hepatobiliary system,
and GGT activity is elevated in any and all forms of liver disease. It is highest in cases of intra- or
post-hepatic biliary obstruction, reaching levels some 5 to 30 times normal. It is more sensitive than
alkaline phosphatase (ALP), leucine aminopeptidase, aspartate transaminase, and alanine
amintotransferase in detecting obstructive jaundice, cholangitis and cholecystitis; its rise occurs earlier
than with these other enzymes and persists longer. Only modest elevations (2-5 times normal) occur in
infectious hepatitis, and in this condition GGT determinations are less useful diagnostically than are
measurements of the transaminases. High elevations of GGT are also observed in patients with either
primary or secondary (metastatic) neoplasms. Elevated levels of GGT are noted not only in the sera of
patients with alcoholic cirrhosis but also in the majority of sera from persons who are heavy drinkers.
Studies have emphasized the value of serum GGT levels in detecting alcohol-induced liver disease.
Elevated serum values are also seen in patients receiving drugs such as phenytoin and phenobarbital, and
this is thought to reflect induction of new enzyme activity. Normal values are observed in various muscle
diseases and in renal failure. Normal values are also seen in cases of skeletal disease, children older that 1
year and in healthy pregnant women-conditions in which ALP is elevated.
Useful For: Diagnose and monitor hepatobiliary disease, it is currently the most sensitive enzymatic
indicator of liver disease To ascertain whether observed elevations of alkaline phosphatase are due to
skeletal disease (normal gamma-glutamyltransferase: GGT) or reflect the presence of hepatobiliary
disease (elevated GGT) A screening test for occult alcoholism
Interpretation: An elevation of gamma-glutamyltransferase (GGT) activity is seen in any and all
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