Specimen

Blood

Collection Medium:

Minimum:

Collect blood in a lavender top (EDTA) tube(s) from a fasting (4 hour) 
patient. Send 5.0 mL of EDTA whole blood refrigerated.
Absolute minimum:  2.0 mL

Rejection Criteria:

Specimen cannot be frozen.

Delivery Instructions:

Submit specimen to laboratory as soon as possible after collection.

Analytic Time:

1 week

Reference Range:

> or = 18.5 U/g of hemoglobin

Comments:

Patient's age is required on request form for processing.

Useful for:
1) Diagnosis, carrier detection, and determination of genotype of GALT 
deficiency, the most common case of galactosemia

2) Differentiating D/G mixed heterozygotes from classical galactosemia

3) Confirming results of new born screening programs

Interpretation of GALCON
This test detects four of the most frequently encountered classical 
galactosemia alleles (Q188R, S135L, K285N, and L195P), as well as the 
N314D Duarte and L218L Los Angeles variants.

The laboratory provides an interpretation of the results, including 
GALT enzyme activity, genotype, and biochemical phenotype, if 
necessary.  This interpretation provides an overview of the results and 
their significance, a correlation to available clinical information, 
elements of differential diagnosis, and recommendations for additional 
testing.

When GALT enzyme activity is in the normal range (>18.5 U/g 
hemoglobin), the laboratory will only test for the Los Angeles and 
Duarte variants, since the probability of having the G mutant allele 
would be unlikely.  Any specimen where enzyme activity is <18.5 U/g 
hemoglobin will be analyzed for the presence of the four mutations 
associated with classic galactosemia, as well as the two variants 
(Duarte and Los Angeles).

Galactosemia occurs in patients who enzyme levels are extremely low.

CAUTION:  This assay is not useful for monitoring dietary compliance by 
galactosemics, "GAL1P".

CPT Code:

82664, 82775, 83890, 83896(x6), 83898(x6), 83912

See also:
Gal-1-Phos Urdyltrns Phenotype, RBC, Whole Blood

See Additional Information:
Fasting Specimen Requirements