Carbohydrate Deficient Transferrin (CDT)

Diagnostic Use

Carbohydrate deficient transferrin (CDT) can be used to assess a patient's chronic alcohol consumption. The test does not correlate with the amount of alcohol consumed, but relates to the prolonged consumption of large quantities of alcohol. A single episode of heavy drinking will not elevate CDT levels.
CDT is reported as a percentage of total transferrin to reduce the effects of gender and varying transferrin concentrations.
CDT has a long half-life of 15 days. Under conditions of total abstinence it may take 1-2 months for CDT levels to return to normal.
The most reliable interpretation is obtained with a series of CDT tests to detect trends, with the tests being performed at 1-2 month intervals to allow for the long half-life of this protein.
False positive CDT results may occur in patients with severe liver disease, autoimmune hepatitis, biliary cirrhosis, liver cell cancer, haemochromatosis, transferrin variants and rarely congenital disorders of glycosylation.

Department

Protein Lab

Delphic Registration Code

CDT

Synonyms

%CDT
CDT%

Turnaround Time

1 week

Test Code

7448

Specimen Type

• Serum

Specimen Requirements

Tube/Container Type:

Preferred

• Serum (Red Cap)

Acceptable

• SST II (Gold Cap)

Preferred Sample Volume (ml)

0.5

Minimum Sample Volume (ml)

0.25

No of Samples Required

1

Interferences

PLASMA samples are not acceptable - presence of fibrinogen causes interference.

Aliquot Instructions

Sample Type

• Serum

Minimum Volume (ml)

0.5

Transport to Lab

Chilled (2 - 8 degrees Celsius)
If overnight - Chilled (2 - 8 degrees Celsius)

Interpretation

Chronic alcoholism causes a transient change in the glycosylation pattern of transferrin where the relative amount of disialo transferrin (carbohydrate deficient transferrin: CDT) is increased.

CDT typically normalizes within several weeks of abstinence of alcohol use. However, it is important to recognize that there are other causes of abnormal CDT levels, which include congenital disorders of glycosylation and other genetic and nongenetic causes of acute or chronic liver disease.

CDT testing alone is not recommended for general screening for alcoholism; however, when combined with other methods (ie, gamma-glutamyltransferase, mean corpuscular volume, patient self-reporting, ethylglucuronide analysis), clinicians can expect to identify the majority of patients who consume a large amount of alcohol.

Reference Intervals

Reference Interval CDT-IFCC	Classification
< 1.8 %	Normal result
1.8 – 2.0 %	Inconclusive
> 2.0 %	Positive result

Measurement uncertainty 10 %

Test Method

CDT-IFCC by Capillary Electrophoresis

Non-Funded Test Cost

$81.56 (Exclusive of GST)

Billing Code

7448

Contact Information

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