Specimen:

Blood

Collection Medium:

Minimum:

Preferred minimum: 5 mL heparinized whole blood
Absolute minimum: 2 mL heparinized whole blood

Delivery Instructions:

Submit specimen to laboratory as soon as possible after collection.

Testing Schedule:

Testing performed on Tuesdays and Thursdays.

Analytic Time:

2 weeks

Reference Range:

Non-galactosemic:                           5-49  mcg/g of hemoglobin
Galactosemic on galactose restricted diet: 80-125 mcg/g of hemoglobin
Galactosemic on unrestricted diet:           >125 mcg/g of hemoglobin

Comments:

Three types of enzymatic deficiencies, galactokinase, 
galactose-1-phosphate uridyltransferase (GPUT), and uridine diphosphate 
(UDP) galactose-4-epimerase are responsible for galactosemia, an 
autosomal recessive inborn error of galactose metabolism.

Clinical Information:
The most common form of galactosemia (classic galactosemia) is caused 
by homozygous inheritance of abnormal GPUT phenotypic designation (GG) 
and results in absence of GPUT activity and accumulation of 
galactose-1-phosphate (G-1-P) in erythrocytes.  Classic galactosemia is 
characterized by failure to thrive, vomiting, liver disease, cataracts, 
and developmental delay.

Useful for:
Monitoring dietary therapy for classic galactosemia (total GPUT 
deficiency), galactosemia-Duarte (GD) patients, or rarely, patients 
with UDP galactose-4-epimerase deficiency.

Interpretation:
The reference values provided are for nongalactosemics and for 
galactosemic patients on a galactose-restricted diet.

The goal of treatment of a galactosemic patient is to have G-1-P levels 
as low as possible, but no higher than 125 mcg/g of hemoglobin.

Cautions:
Not a screening test for galactosemia

Methodology:

Ultraviolet, Enzymatic

This assay is a quantitative measure of the galactose-1-phosphate and 
is useful for monitoring the dietary management of galactosemics.  This 
assay should not be used for the diagnosis of galactosemia.

CPT Code:

84378