Galactosemia, GALT Gene, Variant Panel, Varies
Use
This test serves as a second-tier test to confirm a diagnosis of galactosemia identified through enzymatic testing or newborn screening. It is useful for carrier testing among family members with a known genotype within the panel and is instrumental in resolving Duarte and Los Angeles variant genotypes. Galactosemia is an autosomal recessive disorder caused by a deficiency in any of four enzymes catalyzing the conversion of galactose to glucose, with GALT deficiency being the most common cause. The test aids in assessing variants in the GALT gene, linked to classic galactosemia, which is a potentially life-threatening condition if not treated immediately with a galactose-restricted diet. Despite treatment, developmental delays and reproductive issues may occur, placing an emphasis on accurate diagnosis.
Special Instructions
A previous hematopoietic stem cell transplant from an allogenic donor will interfere with testing. Maternal cell contamination studies are recommended for postnatal umbilical cord whole blood specimens to ensure accurate results. Informed consent is required for genetic testing for New York clients. Specimens from other locations without CLIA certification may not be suitable. Clients are advised to complete forms available on the Mayo Clinic site to facilitate testing. Carrier testing results should be interpreted in the context of the patient's family history and biochemical results.
Limitations
The test will not detect all disease-causing variants associated with galactosemia, and a negative result does not eliminate the risk due to undetected variants or the rare chance of false-negative results. Not all targeted variants have positive controls available, and the negative predictive value of these targets is unknown. Cautions include potential result interference from bone marrow transplants, requiring specialized testing considerations. Additional tests may be warranted if results do not align with clinical observations, and the detection of DNA variants of unknown significance can occur.
New York Approved
Methodology
Microarray (SNP Array)
Biomarkers
LOINC Codes
- 42318-6
- 50397-9
- 82939-0
- 69047-9
- 48767-8
- 85069-3
- 31208-2
- 18771-6
Result Turnaround Time
7-21 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
3 mL
Minimum Volume
Not provided
Container
Lavender top (EDTA) or yellow top (ACD)
Collection Instructions
Invert several times to mix blood. Send whole blood specimen in original tube. Do not aliquot. Whole blood collected postnatal from an umbilical cord is acceptable. Specimens are preferred to be received within 4 days of collection. Extraction will be attempted for specimens received after 4 days, and DNA yield will be evaluated. For postnatal umbilical cord specimens, maternal cell contamination studies are recommended. A maternal blood specimen is required to complete these studies.
Patient Preparation
A previous hematopoietic stem cell transplant from an allogenic donor will interfere with testing.
Causes for Rejection
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 4 days |
| Refrigerated | 4 days |
| Frozen | 4 days |