Galactosemia (GALT) Enzyme Activity and 9 Mutations
Ordering Recommendation

Initial test to diagnose or rule out classic galactosemia. Recommended carrier testing for galactosemia.

Enzymatic/Polymerase Chain Reaction/Single Nucleotide Extensions
Mon, Wed, Fri
7-10 days
New York DOH Approval Status
This test is New York DOH approved.
ARUP Consult®
Disease Topics
Specimen Required
Patient Preparation
Lavender (EDTA), pink (K2EDTA), or green (sodium heparin). 
Specimen Preparation
Do not freeze. Transport 10 mL whole blood. (Min: 3 mL) 
Storage/Transport Temperature
Unacceptable Conditions
Frozen or room temperature specimens. 
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:
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.

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

Statement C: Compliance Statement C: For human genetic inheritable conditions and mutations. This test was developed and its performance characteristics determined by ARUP Laboratories. The U. S. Food and Drug Administration has not approved or cleared this test; however, FDA clearance or approval is not currently required for clinical use. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online.

Hotline History
Component Test Code*Component Chart NameLOINC
0051171Galactosemia (GALT) DNA Pan,G1PUT Spec
0051177Galactosemia - Ethnicity42784-9
0051178Galactosemia - Symptoms
0051179Galactosemia - Abnormal Newborn Screen
0051180Galactosemia - Family History8670-2
0051182Galactosemia (GALT) Allele 142940-7
0051183Galactosemia (GALT) Allele 242941-5
0051187Galactosemia (GALT) DNA Pan,G1PUT Interp
0080125Galac-1-Phos Uridyltransferase10970-2
* 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 view this test within the Laboratory Test Directory found at
  • Galactosemia Carrier Testing
  • Galactosemia Confirmation Test
  • Galactosemia genotyping