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Test ID GALK Galactokinase, Blood

Useful For

Diagnosis of galactokinase deficiency, the second most common cause of galactosemia

Testing Algorithm

See Galactosemia Testing Algorithm in Special Instructions.

Method Name

Radioisotopic

Reporting Name

Galactokinase, B

Specimen Type

WB Sodium Heparin

Specimen must arrive within 48 hours of draw.

 

Container/Tube: Green top (sodium heparin)

Specimen Volume: 5 mL

Additional Information: Date of draw is required.

Forms: New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
WB Sodium Heparin Refrigerated 48 hours

Clinical Information

Galactokinase (GALK) deficiency is the second most common form of galactosemia, affecting approximately 1/250,000 live births, with a higher frequency in the Romani population. Individuals with GALK deficiency have a milder clinical presentation than that seen in patients with classic galactosemia, galactose-1-phosphate uridyltransferase (GALT) deficiency. The major clinical manifestation is bilateral juvenile cataracts.

 

GALK deficiency is treated with a lactose-restricted diet. Early treatment may prevent or reverse the formation of cataracts.

 

In GALK deficiency, erythrocyte galactose-1-phosphate levels are generally normal and plasma galactose levels are generally elevated. The diagnosis is established by demonstrating deficient GALK enzyme activity in erythrocytes. Testing for GALK deficiency should be performed when there is a suspicion of galactosemia, either based upon the patient's clinical presentation or laboratory studies and GALT deficiency has been excluded. Specimens sent for GALT analysis may be used for GALK testing if the original specimen was received in the laboratory within 48 hours of draw.

 

GALK deficiency is caused by mutations in the GALK1 gene. Gene analysis is available from some commercial laboratories. Contact Mayo Medical Laboratories for recommendations or contact information for laboratories that offer this testing.

 

See Galactosemia Testing Algorithm in Special Instructions.

Reference Values

<2 years: 20.1-79.8 mU/g of hemoglobin

≥2 years: 12.1-39.7 mU/g of hemoglobin

Cautions

It is important to notify the laboratory if the patient has been transfused prior to specimen collection. The results of testing performed in erythrocytes are invalid following a transfusion, including analysis of enzymes, biochemical phenotyping, or galactose-1-phosphate.

 

The most common cause of galactosemia is GALT deficiency (see GALT / Galactose-1-Phosphate Uridyltransferase [GALT], Blood). In most cases, GALT deficiency should be ruled out prior to evaluating for GALK deficiency.

Day(s) Performed

Alternating Wednesdays; 9 a.m.

Report Available

14 days

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

82759

NY State Approved

Yes