Galactosemia Confirmation Test
| Order Code: | GALCON |
| Epic Lab Code: | LAB3194 |
| Order Form: | A-1a Miscellaneous Request or Epic Req |
Commercial Mail-out Laboratory
6240 RCP
356-3527
6240 RCP
356-3527
Specimen:
Blood
Collection Medium:
 | and | |
| Lavender top tube 4 mL (EDTA) | Lavender top tube 4 mL (EDTA) |
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:
4 days upon receipt at references laboratory
Reference Range:
> or = 18.5 U/g of hemoglobin
Interpretive Data:
The laboratory provides an interpretation of the results, including
GALT enzyme activity and genotype, 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.
Any specimen where enzyme activity is <18.5 U/g hemoglobin will be analyzed for the presence of the 4 mutations associated with classic galactosemia, as well as the 2 variants (Duarte and LA).
This test detects 4 of the most frequently encountered classic galactosemia alleles (Q188R, S135L, K285N, and L195P), as well as the N314D Duarte and L218L LA variants. A high proportion (20%) of patients with classic galactosemia have a private mutation. Since our assay does not investigate for the presence of private mutations, when GG, DG, or NG genotype is predicted by enzymatic studies and the current panel does not identify a mutation, molecular sequencing may be indicated.
Any specimen where enzyme activity is <18.5 U/g hemoglobin will be analyzed for the presence of the 4 mutations associated with classic galactosemia, as well as the 2 variants (Duarte and LA).
This test detects 4 of the most frequently encountered classic galactosemia alleles (Q188R, S135L, K285N, and L195P), as well as the N314D Duarte and L218L LA variants. A high proportion (20%) of patients with classic galactosemia have a private mutation. Since our assay does not investigate for the presence of private mutations, when GG, DG, or NG genotype is predicted by enzymatic studies and the current panel does not identify a mutation, molecular sequencing may be indicated.
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
Preferred test to evaluate for possible diagnosis of galactosemia,
routine carrier screening, and follow-up of abnormal newborn screening
results. Comprehensive reflex test begins with quantitative galactose-1-
phosphate uridyltransferase (GALT) enzyme analysis. If quantitative
GALT enzyme value is consistent with a diagnosis of or carrier status
for galactosemia, DNA analysis of the GALT gene is performed
to detect the 4 most frequently encountered classic galactosemia
alleles (Q188R, S135L, K285N, and L195P) in addition to the N314D
(Duarte) and L218L (Los Angeles) variants.
Test
Limitations:
This assay is not useful for monitoring dietary compliance by
galactosemics.
This assay will not detect all of the mutations that cause galactosemia. Therefore, the absence of a detectable mutation(s) does not rule out the possibility that an individual is a carrier of or affected with this disease.
Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.
Many disorders may present with symptoms similar to those associated with galactosemia. Therefore, biochemical testing is performed to establish the diagnosis of galactosemia prior to DNA analysis.
This assay will not detect all of the mutations that cause galactosemia. Therefore, the absence of a detectable mutation(s) does not rule out the possibility that an individual is a carrier of or affected with this disease.
Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.
Many disorders may present with symptoms similar to those associated with galactosemia. Therefore, biochemical testing is performed to establish the diagnosis of galactosemia prior to DNA analysis.
Methodology:
GALT converts uridine diphosphoglucose (UDPG) to UDP-galactose. The
amount of UDPG consumed is measured by oxidizing UDPG with concomitant
generation of NADPH from NADP (UDPG-dehydrogenase), which is measured
at 340 nm. (Beutler E, Baluda MC: Improved method for measuring
galactose-1-phosphate uridyl transferase activity of erythrocytes. Clin
Chim Acta 1966
March;13(3):369-379)
A real-time PCR-based assay using the LightCycler detects 6 alterations: Q188R, L195P, S135L, K285N, L218L, and N314D. (Dobrowolski SF, Banas RA, Suzow JG, et al: Analysis of common mutations in the galactose-1-phosphate uridyl transferase gene. J Mol Diagn 2003;5:42-47)
A real-time PCR-based assay using the LightCycler detects 6 alterations: Q188R, L195P, S135L, K285N, L218L, and N314D. (Dobrowolski SF, Banas RA, Suzow JG, et al: Analysis of common mutations in the galactose-1-phosphate uridyl transferase gene. J Mol Diagn 2003;5:42-47)
CPT Code:
"Galactose-1-Phosphate Uridyltransferase (GALT), Blood"
82775
"Galactosemia Gene Analysis (6-Mutation Panel)"
83890/Molecular isolation or extraction (if appropriate)
83896/x6 Nucleic acid probe, each (if appropriate)
83898/x6 Amplification, target, each nucleic acid sequence (if
appropriate)
See also:
Gal-1-Phos Urdyltrns Phenotype, RBC, Whole Blood
Gal-1-Phos Urdyltrns Phenotype, RBC, Whole Blood
See Additional Information:
Fasting Specimen Requirements
Fasting Specimen Requirements