Gel (SST) tubes are unsuitable for this assay
| less than or equal to 1.7% | normal |
| >1.7% to 2.0% | inconclusive |
| > 2.0% | positive - consistent with alcohol abuse or excessive alcohol consumption |
Uncertainty of Measurement: 10%
Sebia capillary electrophorisis
Carbohydrate deficient transferrin can be used, in conjunction with other indicators, to assess a patient's chronic alcohol consumption. It is not increased by a single episode of heavy alcohol consumption.
CDT is reported as a percentage of total transferrin, to reduce the effects of gender and varying transferrin concentrations.
95% of non-drinkers and individuals with normal drinking patterns will have CDT values below 1.7%. Values greater than 1.7% usually indicate a consumption of more than 60 g of ethanol per day over a period of at least one week. Note that 5% of individuals will therefore have a %CDT of >1.7% without excessive drinking. Therefore CDT values should be interpreted with caution.
In the case of complete abstinence in a patient with previously elevated concentrations, it can take up to two months for the %CDT to return to normal.
Although the %CDT is probably the most reliable indicator we have of alcohol consumption, it correlates poorly with the quantity of alcohol consumed. It also correlates poorly with other markers of alcohol consumption, and so these other markers (particularly GGT - gamma Glutamyl Transferase ) also need to be considered when interpreting the result.
If both GGT and %CDT are normal, then there is probably no alcohol misuse.
If both are elevated, then there probably is misuse.
Other combinations (one normal, one abnormal) makes the result questionable.
False positive % CDT results may occur in patients with severe liver disease (any cause), autoimmune hepatitis, biliary cirrhosis, liver cell cancer, haemochromatosis, genetic transferrin variants and the rare CDG syndrome.
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 - 15 days).
References:
1. Arndt T. Carbohydrate deficient transferrin as a marker of chronic alcohol abuse: a critical review of pre-analysis, analysis and interpretation. Clin Chem 47: 13- 27, 2001.
2. Anton RF et al. Comparison of Bio-Rad % CDT TIA and CDTect as laboratory markers of heavy alcohol use and their relationship with gamma-glutamyl transferase. Clin Chem 47: 1769-75, 2001.
3. DiMartini et al. CDT in abstaining patients with end-stage liver disease. Alcohol Clin Exp Res 25(12): 1729-33, 2001
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427
Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427
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Instructions for Referral |
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| Aliquot Instructions |
Serum (NOT gel SST, plain only) Minimum 250 uL, Preferred 500 uL. Refrigerate. |
| Aliquot Transport: | Refrigerated |
Samples are stable for:
Room temperature - up to 48 hours
Refrigerated - up to 10 days
Frozen - up to 12 months