Galactose-1-Phosphate Uridyltransferase (GALT), Blood Test
The GALT test measures galactose-1-phosphate uridyltransferase (GALT) enzyme activity and galactose-1-phosphate accumulation in a whole blood sample. Quest describes these as markers associated with galactosemia, an inherited disorder of galactose metabolism.
About this test
GALT is an enzyme that converts galactose to glucose, and Quest describes galactosemia — an inherited, autosomal recessive disorder — as most commonly caused by a deficiency of this enzyme. This test measures GALT enzyme activity and/or the buildup of galactose-1-phosphate in red blood cells, using an enzyme reaction followed by liquid chromatography/tandem mass spectrometry on a whole blood sample collected in an EDTA tube.
Quest lists this test as used both as follow-up to a newborn screening result, to help evaluate a possible galactosemia finding, and for ongoing monitoring of galactose-1-phosphate levels to assess how well a galactose-restricted diet is being followed. People come to it either through that newborn-screening pathway or as part of continued monitoring, and a clinician reads the result in the context of which of those two situations applies.
Test details
| Collection | Quest patient service center |
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Quest resources
Additional details
What this test looks at
Quest lists this test under several related names — including G1PUT, Gal-1-P, G-1-P-U Trans, G1PU and Galactose 1 P — all referring to the same GALT enzyme and galactose-1-phosphate measurement. The result includes an interpretation alongside the enzyme and metabolite values, meant to be read by the ordering clinician.
This test isn't part of the Celio Health store at the moment, so it can't be ordered or requested here. The test menu lists everything that can.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What does the GALT test measure?
It measures GALT enzyme activity and/or galactose-1-phosphate accumulation in red blood cells, using an enzyme reaction followed by liquid chromatography/tandem mass spectrometry on a whole blood sample.
How is the sample collected?
The test uses a whole blood sample collected in an EDTA tube.
Do I need to prepare for this test?
No preparation instructions are listed for this test, though people follow any instructions their ordering clinician provides.
Why might this test be ordered?
Quest lists it as used for follow-up to a newborn screening result and for ongoing monitoring of galactose-1-phosphate levels to assess compliance with a galactose-restricted diet.
Is galactosemia serious?
Quest notes that, left untreated, galactosemia can be life-threatening, and that it is managed with a galactose-restricted diet; a clinician interprets this test's result within that full clinical picture.