Preferred minimum: 5 mL heparinized whole blood from fasting patient Absolute minimum: 2 mL heparinized whole blood from fasting patient

<2 years: 20.1-79.8 mU/g Hemoglobin Greater than or equal to 2 years: 12.1-39.7 mU/g Hemoglobin

Whole blood to be washed at reference laboratory. If specimen cannot arrive within 48 hours, please send washed erythrocytes. Draw blood in a green top (heparin) tubes(s) from a fasting patient (4 hour preferred, nonfasting acceptable), and send 5.0 mL of heparinized whole blood refrigerated. Clinical information: Three clinically important inborn errors of galactose metabolism that result in galactosemia have been described. The genetic disturbance is expressed as a deficiency of galactokinase, galactose-1-phosphate uridyltransferase, or UDP galactose-4-epimerase, the enzymes catalyzing the reactions in converting galactose to glucose. The transferase deficiency is the most common. Galactokinase deficiency results in a milder variant of galactosemia than that which results from GALT deficiency. The epimerase deficiency is like the kinase deficiency and is much more rare than the transferase deficiency. Useful for: Diagnosis of the second most common cause of galactosemia (ie, galactokinase deficiency). Interpretation: Values <20.1 mU/g of hemoglobin suggest galactokinase deficiency.