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Testing for CDG

Individuals who exhibit signs and symptoms of CDG should be referred for diagnostic testing to confirm they have this condition. Most CDG patients can be diagnosed by a simple blood test to analyze the glycosylation status of transferrin (Tf). Abnormal Tf is detected by isoelectric focusing (IEF), or by electrospray ionization-mass spectrometry (ESI-MS). Once CDG is diagnosed, further testing is required to determine the type of CDG.

Diagnosis of CDG Physician Information:
Test Name: Carbohydrate Deficient Transferrin Test
Method: ESI-MS method superior to IEF, CE (Capillary Electrophoresis), or HPLC (High Performance Liquid Chromatography)
Laboratory: Mayo Medical Laboratories Test (82414); CPT Code 82373
Requirments: Requires: 0.1 ml of serum
Detection: Will detect all known CDG-I types, many CDG-x. Will not detect: CDG-IIb, CDG IIc, CDG-IIf. Test may need to be rerun if done less than 2 weeks of age.

Physician Contact:
Mayo Medical Laboratories
Request: Carbohydrate Deficient Transferrin, serum. Test code 82414.
Phone: 1-800-533-1710
Fax: 1-507-284-4542
E-mail: mml@mayo.edu
Web: www.mayoreferenceservices.org/mrs/index.asp

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Prenatal Testing

Many families who have a child with CDG want to know what their risk is of having another child with CDG with another pregnancy. This risk can be assessed by knowing that CDG is a recessively inherited disease. This means that, although each parent carries two genes for the CDG function, one of them doesn't work correctly. The functional single gene in the parent protects them from having CDG. A child with CDG has inherited two of these non-working genes, one from each parent. Usually there is a 1:4 risk of having a second child with CDG-Ia, but recent work shows that the ratio is closer to 1:3. This higher incidence is surprising, and so far, it has only been shown for CDG-Ia. Families are encouraged to contact a genetics consultant. A genetics doctor/counselor can help to explain the genetic risk for each family and the risk in future pregnancies.