Galactose-1-phosphate
Galactosemia: Galactose-1-Phosphate Analysis
Galactosemia: Galactose-1-Phosphate Analysis
Galactosemia is an inborn error of carbohydrate metabolism caused by the deficiency of galactose-1-phosphate uridyl transferase (GALT), which performs the second enzymatic step in the conversion of galactose to glucose-1-phosphate. As a result of the enzyme deficiency, excess galactose is excreted in the urine and the substrate for GALT, galactose-1-phosphate, accumulates throughout the body. The measurement of galactose-1-phosphate is performed to confirm a new diagnosis of galactosemia and to periodically monitor the effectiveness of treatment in patients known to have the disease.
Galactosemia
Clinical Information
Manifestations of the galactosemia appear within days of the initiation of milk feedings, and include vomiting, jaundice and failure to thrive. If left untreated for a prolonged period of time, patients will develop hepatomegaly, cataracts and intellectual disability. Speech delay and premature ovarian failure are also observed in many galactosemia patients, even in those who are diagnosed early and put on treatment.
Technical Information
NADH is measured by spectrophotometry at absorbance of 340 nm. NADH is produced when galactose is converted to galactonolactone by galactose dehydrogenase either after treatment with alkaline phosphatase (galactose-1-phosphate + galactose) or without treatment with alkaline phosphatase (galactose only).
Specimen Requirements
The accepted sample type for this test is whole blood, and requires a minimum of 5 mL (preferably 7-10 mL) whole blood collected in a sodium heparin tube.
Transport Instructions
Whole blood should be shipped at ambient temperature.
Associated Tests
Connect With Our Experts
Call 1-800-473-9411 to speak with our team of laboratory genetic counselors for questions or additional information.
Robin Fletcher, MS, CGC
Falecia Thomas, MS, CGC
Alex Finley, MS, CGC