Galactosemia (GALT) Enzyme Activity and 9 Mutations
0051175
Ordering Recommendation
Initial test to diagnose or rule out classic galactosemia. Recommended carrier testing for galactosemia.
Mnemonic
GALTPAN
Methodology
Enzymatic/Polymerase Chain Reaction/Single Nucleotide Extensions
Performed
Tue, Thu
Reported
7-10 days  
New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
  
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.  
Unacceptable Conditions
Frozen or room temperature specimens.  
Remarks
 
Stability
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. Diagnostic errors can occur due to rare sequence variations.
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





See Compliance Statement C: www.aruplab.com/CS
Statement C: The performance characteristics of this test were validated by ARUP Laboratories. The U.S. Food and Drug Administration (FDA) has not approved or cleared this test; however, FDA approval or clearance is currently not required for clinical use of this test. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions. ARUP is authorized under Clinical Laboratory Improvement Amendments (CLIA) and by all states to perform high-complexity testing.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
 
Note
 
CPT Code(s)
82775, 81401
Components
Component Test Code*Component Chart Name
0051171Galactosemia (GALT) DNA Pan,G1PUT Spec
0051177Galactosemia - Ethnicity
0051178Galactosemia - Symptoms
0051179Galactosemia - Abnormal Newborn Screen
0051180Galactosemia - Family History
0051182Galactosemia (GALT) Allele 1
0051183Galactosemia (GALT) Allele 2
0051187Galactosemia (GALT) DNA Pan,G1PUT Interp
0080125Galac-1-Phos Uridyltransferase
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • GALT DNA
  • Galactosemia Carrier Testing
  • Galactosemia Confirmation Test
  • Galactosemia genotyping