CDT, Carbohydrate Deficient Transferrin (T493) [Back]
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| RISK ASSESSMENT VALUE: |
Transferrin is a glycoprotein made in the liver whose chief function is to transport iron. During creation, carbohydrates (sugars) become attached to the molecule. In the presence of heavy daily alcohol use, fewer sugars are attached creating a higher percentage of carbohydrate deficient transferrin. The amount of alcohol needed for the test to become positive is usually 4 or more drinks every day in men and at least 3 in women over the prior 2-4 weeks reflecting the ½ life of transferrin in the blood.
Commercial CDT kits are used by the insurance labs. Both anion exchange and capillary electrophoresis (CE) kits are available and may be in use. CE has demonstrated high specificity equivalent to the original isoelectric focusing (IEF). Anion exchange has lower specificity and may require a confirmation step to have adequate predictive value in a relatively low risk population such as insurance applicants. The positive predictive value of even the highly specific CE test is less than .5 in insurance applicants unless history or other laboratory abnormalities such as an elevated GGT is present. Even then, the best you might expect is .75 (correct 3 times in 4) which is in keeping with other underwriting data such as EKGs on which risk decisions are made. Sensitivity for heavy alcohol is moderate so negative CDTs do not rule out such use and the test is insensitive for binge drinking only.
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| NORMAL RESULTS: |
Negative (values)
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| ABNORMAL RESULTS: |
Positive (values).
Positive results can be the result of severe liver disease which should be apparent on the other lab and genetic variants.
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| ADDITIONAL TESTS: |
History, MVR, serum alcohol
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| SAMPLE NEEDED: |
Separated serum from red or mottled stopper tube.
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| SAMPLE STABILITY: |
Five days at room temperature; indefinitely when frozen at -20.
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| METHOD & INSTRUMENT: |
Microparticle Enzyme Immunoassay, Roche E-170.
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| PURPOSE: |
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| PROFILE INCLUDES: |
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| RISK RANGE & UNITS: |
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