ARUP's Laboratory Test Directory

Galactosemia (GALT) Enzyme Activity and 9 Mutations : 0051175
[ image for: Patient History For Galactosemia]
Patient History For Galactosemia
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Additional Technical Information


Mnemonic: GALTPAN

Ordering Recommendation: Diagnostic testing for galactosemia or carrier screening for galactosemia.
Methodology: Enzymatic/Polymerase Chain Reaction/Single Nucleotide Extensions
Performed: Tue, Thu
Reported: 7-10 days
Specimen Required: Collect: Lavender (EDTA), pink (K2EDTA), or green (sodium heparin).

Specimen Preparation: Do not freeze. Transport 10 mL whole blood. (Min: 3 mL)

Storage/Transport Temperature: Refrigerated.

Remarks:

Unacceptable Conditions: Frozen or room temperature specimens.

Stability (collection to initiation of testing): Ambient: Unacceptable; Refrigerated: 5 days; Frozen: Unacceptable
Reference Interval:
By report
Interpretive Data: One U/g Hb is equivalent to one umol/hour/gram of hemoglobin (umol/hr/g Hb).

Background Information for Galactosemia (GALT) Enzyme Activity and 9 Mutations:
Characteristics: Affected infants present at 3-14 days old with poor feeding, vomiting, diarrhea, jaundice, lethargy progressing to coma, and abdominal distension with hepatomegaly usually followed by progressive liver failure. Patients with galactosemia are also at increased risk for E. coli or other gram-negative neonatal sepsis. Diagnosis is made by measuring GALT enzyme activity in red blood cells.
Incidence: Approximately 1 in 30,000 to 60,000 of classic galactosemia in Caucasian, varies in other populations.
Inheritance: Autosomal recessive
Penetrance: 100 percent for severe GALT mutations
Cause: Mutations in the GALT gene.
Mutations Tested: Seven GALT gene mutations (Q188R, S135L, K285N, T138M, L195P, Y209C, and IVS2-2 A>G) and two variants (N314D and L218L).
Clinical Sensitivity DNA: Approaches 80 percent in Caucasians but reduced in other ethnic groups.
Methodology DNA: Polymerase chain reaction followed by single nucleotide extension (SNE) and capillary electrophoresis.
Analytical Sensitivity DNA: 99 percent for mutations listed.
Limitations DNA: GALT gene mutations, other than the 9 targeted, will not be detected. Rare diagnostic errors can occur due to primer site mutations.
Methodology Enzymatic: Spectrophotometric quantitation of enzyme activity in red blood cells.

This test is performed pursuant to an agreement with Roche Molecular Systems, Inc.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online at www.aruplab.com



Counseling and informed consent are recommended for genetic testing. Consent forms are available online at www.aruplab.com.

See Compliance Statement C: www.aruplab.com/CS
CPT Code(s): 82775, 81401