Lab Information Manual

Laboratory:

Clinical Biochemistry (METABOLIC)

Test Name:

GALACTOSE-1-PHOSPHATE URIDYLTRANSFERASE (GALT), Reflex test - (B)

Test Code: MISC

Clinical Information:

Test Indications: Preferred test to evaluate for a possible diagnosis of galactosemia, carrier detection, and follow-up of abnormal newborn screening results. Galactose-1-phosphate uridyltransferase (GALT) deficiency is the classical and most common cause of galactosemia.

The complete or near-complete deficiency of GALT enzyme is life threatening if left untreated. Complications in the neonatal period include failure to thrive, liver failure, sepsis and death; even with survival, long-term intellectual disability can occur. Galactosemia is treated by a galactose-restricted diet which allows for rapid recovery from the acute symptoms.

THIS IS A REFLEX TEST (Mayo Clinic Laboratories).
Any specimen where GALT enzyme activity is less than 24.5 nmol/h/mg of hemoglobin will be analyzed for the presence of 14 mutations associated with classic galactosemia, as well as the 2 variants (Duarte and Los Angeles).

A PCR-based assay utilizing Sequenom Mass Array platform is used to test for the presence of the following 14 mutations in the GALT gene:
-119_-116delGTCA, D98N, S135L, T138M, M142K, F171S, Q188R, L195P, Y209C, K285N, N314D, Q344K, c.253-2A>G and 5 kb deletion.

This assay will not detect all mutations that cause galactosemia. Therefore, the absence of a detectable mutation does not rule out the possibility that an individual is a a carrier of or affected with this disease.

Restricted to Manitoba Medical Geneticists, Gastro-Enterologists, Neonatalogists/Pediatrics

For questions/help: please communicate with the biochemical geneticist.

Collection Devices:

Preferred Device:	1 - EDTA 4 mL NO GEL Tube(s) - Full Tube Collection EDTA 4 mL NO GEL Tube(s) - Full Tube Collection Manufacturer: Becton Dickinson & Company Catalogue #: 367861 - Store: Refrigerated preferred, Ambient is acceptable. Reject due to: Gross hemolysis
Alternate Device:	1 - ACD Solution B - 6 mL Tube(s) - Full Tube Collection ACD Solution B - 6 mL Tube(s) - Full Tube Collection Manufacturer: Becton Dickinson & Company Catalogue #: 364816

Specimen Required:

Referral:

Store and ship refrigerated to the Metabolic Lab (HSC).

Requisition:

_SH Biochemical Genetics Laboratory Requisition (R250-10-69)

Reference Values:

GALT enzyme activity: Normal >= 24.5 nmol/h/mg of hemoglobin

Availability:

Within 1 Week

This test is performed 3 times per week at Mayo Clinic Laboratories.