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HelpTest Code CDG Carbohydrate Deficient Transferrin for Congenital Disorders of Glycosylation, Serum
Reporting Name
CDG, SPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Useful For
Screening for congenital disorders of glycosylation
This test is not useful for screening patients for chronic alcohol abuse.
Method Name
Affinity Chromatography-Mass Spectrometry (MS)
Ordering Guidance
This test is for congenital disorders of glycosylation. If the ordering provider is looking for evaluation of alcohol abuse, order CDTA / Carbohydrate Deficient Transferrin, Adult, Serum.
If either PMM2-CDG (CDG-Ia) or MPI-CDG (CDG-Ib) is suspected, order PMMIL / Phosphomannomutase and Phosphomannose Isomerase, Leukocytes.
Necessary Information
1. Patient's age is required.
2. Reason for testing is required.
Specimen Required
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 0.1 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Specimen Type
SerumSpecimen Minimum Volume
0.05 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Frozen (preferred) | 45 days | |
| Refrigerated | 28 days | ||
| Ambient | 7 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Reference Values
|
Ratio |
Normal |
Indeterminate |
Abnormal |
|
Transferrin mono-oligo/di-oligo ratio |
≤0.06 |
0.07-0.09 |
≥0.10 |
|
Transferrin A-oligo/di-oligo ratio |
≤0.011 |
0.012-0.021 |
≥0.022 |
|
Transferrin tri-sialo/di-oligo ratio |
≤0.05 |
0.06-0.12 |
≥0.13 |
|
Apo CIII-1/Apo CIII-2 ratio |
≤2.91 |
2.92-3.68 |
≥3.69 |
|
Apo CIII-0/Apo CIII-2 ratio |
≤0.48 |
0.49-0.68 |
≥0.69 |
Interpretation
Positive test results could be due to a genetic or nongenetic condition; additional confirmatory testing is required.
In serum, the bi-antennary transferrin (di-oligo) fraction is the most abundant transferrin isoform. Congenital disorders of glycosylation (CDG)-I generally show increases in mono-oligo- and/or a-oligo transferrin isoforms whereas CDG-II shows elevated increased transferrin with truncated glycans of varying degree depending on the type of defect.(1)
Results are reported as the mono-oligosaccharide/di-oligosaccharide transferrin ratio, the a-oligosaccharide/di-oligosaccharide transferrin ratio, the tri-sialo/di-oligosaccharide transferrin ratio, and the apolipoprotein CIII-1/apolipoprotein CIII-2 ratio, and the apolipoprotein CIII-0/apolipoprotein CIII-2 ratio. The report will include the quantitative results and an interpretation.
The congenital disorders of glycosylation (CDG) profiles are categorized into 5 types:
1. CDG type I profile. Mono-oligosaccharide/di-oligosaccharide transferrin ratio and/or the a-oligosaccharide/di-oligosaccharide transferrin ratio are abnormal. This group should have the apolipoprotein C-III profile within the normal ranges, because the Golgi system is not affected in CDG type I.
2. CDG type II profile. The tri-sialo/di-oligosaccharide transferrin ratio is abnormal. In this category, the apolipoprotein C-III profile will have 2 scenarios:
A. The apolipoprotein CIII-1/apolipoprotein CIII-2 ratio and/or the apolipoprotein CIII-0/apolipoprotein CIII-2 ratio will be abnormal. In this case, the defect is most likely glycan processing in the Golgi apparatus; therefore, a CDG (conserved oligomeric Golgi [COG]) defect or defect that alters the Golgi apparatus is likely.
B. The apolipoprotein CIII-1/apolipoprotein CIII-2 ratio and/or the apolipoprotein CIII-0/apolipoprotein CIII-2 ratio are normal. In this case, the defects most likely do not involve the Golgi system, thus the molecular defect is different.
3. CDG mixed type profile (type I and II together). In this type of profile one can have abnormal tri-sialo/di-oligosaccharide transferrin ratio with the mono-oligosaccharide/di-oligosaccharide transferrin ratio and/or the a-oligosaccharide/di-oligosaccharide transferrin ratio abnormal and may have the apolipoprotein CIII-1/apolipoprotein CIII-2 ratio and the apolipoprotein CIII-0/apolipoprotein CIII-2 ratio normal or abnormal, depending on if the defects involve Golgi apparatus.
4. CDG with normal transferrin and apolipoprotein profile. Some CDG (eg, PGM3, some ALG13, MOGS, NGLY1, SLC35C1, Fut8) pose a problem for their detection. Thus, a careful medical history, physical exam, and analysis of other protein status may be informative for general protein glycosylation defects. If suspicious for either NGLY1- or MOGS-CDG, specific oligosaccharides in urine can be detected (OLIGU / Oligosaccharide Screen, Random, Urine).
5. When the profile cannot be categorized following the above classification, the abnormalities will be reported descriptively according to the molecular mass of the glycan isoform structures.
Reports of abnormal results will include recommendations for additional biochemical and molecular genetic studies to identify the correct form of CDG more precisely. If applicable, treatment options, the name and telephone number of contacts who may provide studies, and a telephone number for one of the laboratory directors (if the referring physician has additional questions) will be provided.
For more information, see Transferrin and Lipoprotein-CIII Isoform Analysis.
Day(s) Performed
Monday, Thursday
Report Available
3 to 6 daysTest Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82373
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| CDG | CDG, S | 90417-7 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| BG160 | Reason for Referral | 42349-1 |
| 31721 | Mono-oligo/Di-oligo Ratio | 35469-6 |
| 31720 | A-oligo/Di-oligo Ratio | 35475-3 |
| 34474 | Tri-sialo/Di-oligo Ratio | 90420-1 |
| 34476 | Apo CIII-1/Apo CIII-2 Ratio | 90421-9 |
| 34475 | Apo CIII-0/Apo CIII-2 Ratio | 90419-3 |
| 50820 | Interpretation | 53808-2 |
| 50822 | Reviewed By | 18771-6 |
Forms
1. Congenital Disorders of Glycosylation (CDG, CDGN, OLIGU) Patient Information
2. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
Special Instructions
Testing Algorithm
Suggested Testing Strategy:
|
Disorder |
Target |
Mayo Test ID |
|
N-glycan, core 1 mucin type O-glycosylation, and conserved oligomeric Golgi (COG) complex defects |
Transferrin, apolipoprotein CIII |
CDG / Carbohydrate Deficient Transferrin for Congenital Disorders of Glycosylation, Serum |
|
N-glycan, core 1 mucin type O-glycosylation, and COG complex defects |
Serum total N-linked glycans, transferrin, and apolipoprotein CIII |
CDGN / Congenital Disorders of N-Glycosylation, Serum (includes test ID CDG) Stepwise analysis of transferrin, apolipoprotein CIII, and serum total N-glycans |
|
alpha-dystroglycanopathies, GPI anchor disorders |
Genes: DAG1, FKRP, FKTN, ISPD, LARGE1, POMGNT1, POMGNT2, POMT1, POMT2 PIGA, PIGL, PIGM, PIGN, PIGO, PIGT, PIGV, PIGW, PGAP2, PGAP3 |
CDGGP / Congenital Disorders of Glycosylation Gene Panel, Varies |
For more information see:
Congenital Disorders of Glycosylation: Screening Algorithm
Epilepsy: Unexplained Refractory and/or Familial Testing Algorithm.