Carbohydrate-deficient transferrin is a useful marker for the detection of chronic alcohol abuse

Potential Drug Interactions with the Percent Carbohydrate-Deficient Transferrin (%CDT) Test, a New Alcohol Biomarker

STUDY OBJECTIVE

To determine the effects of drugs on levels of carbohydrate-deficient transferrin (CDT), using the %CDT test, a new alcohol biomarker, in patients receiving drug therapy for chronic medical conditions such as diabetes mellitus, hypertension, and lipid disorders.

DESIGN

Regression analysis of transformed data.

SETTING

Eight primary care clinics in central Wisconsin.

PATIENTS

Seven hundred ninety-nine primary care patients who were prescribed drug therapy for a variety of chronic illnesses such as diabetes, hypertension, and lipid disorders.

MEASUREMENTS AND MAIN RESULTS

The %CDT level, 30-day history of alcohol consumption, symptoms of alcohol abuse or dependence, health status, and prescribed drugs were determined for each patient. All prescribed drugs that were taken by the patients in the last month were determined by self-report, medical records, or pharmacy records. Of the 799 patients, 89 were receiving drug therapy for diabetes, 299 for hypertension, 209 for both diabetes and hypertension, and 202 for medical conditions other than diabetes or hypertension. A regression analysis was performed after the data were transformed. Alcohol consumption, sex, age, tobacco use, and 20 drug classes were entered into the model. Factors associated with increased %CDT levels were alcohol consumption, female sex, and bupropion use. Two additional drug classes, the angiotensin II receptor blockers and the tricyclic antidepressants, were associated with lower %CDT levels. The effects of bupropion and tricyclic antidepressants on %CDT levels, however, appear to be confounded by alcohol intake.

CONCLUSION

This study suggests that only one of 20 drug classes-the angiotensin II receptor blockers-affected %CDT levels in our primary care sample. Additional research with larger samples is needed to focus on the effects of individual drugs used in general clinical settings on %CDT levels.

Improved Diagnostic Classification of Alcohol Abusers by Combining Carbohydrate-deficient Transferrin and γ-Glutamyltransferase

Background: Biochemical markers can provide objective evidence of high alcohol consumption. However, currently available markers have limitations in their diagnostic performance.

Methods: The diagnostic values of the most frequently used markers [carbohydrate-deficient transferrin (CDT), γ-glutamyltransferase (GGT), aspartate aminotransferase, alanine aminotransferase, and mean corpuscular volume] were studied in an analysis of six different clinical studies (n = 1412) on alcohol abusers and social drinkers. The purpose of the analyses was to determine whether a combination of markers would improve the diagnosis of subjects.

Results: Discrimination between alcohol abusers and social drinkers, as measured by the areas under nonparametric ROC plots, was significantly better (P <0.001) for the new combined marker [γ-CDT = 0.8 · ln(GGT) + 1.3 · ln(CDT)] than for any of the separate markers or combination of CDT or GGT with other markers. The cutoff values for γ-CDT (6.5) can be taken to be the same among males and females.

Conclusions: The combined variable γ-CDT is a powerful tool to discriminate alcohol abusers from social drinkers and is recommended for clinical use.

Carbohydrate-deficient Transferrin as a Marker of Chronic Alcohol Abuse: A Critical Review of Preanalysis, Analysis, and Interpretation

Background: Carbohydrate-deficient transferrin (CDT) is used for diagnosis of chronic alcohol abuse. Some 200–300 reports on CDT have been published in impact factor-listed journals. The aims of this review were to condense the current knowledge and to resolve remaining issues on CDT.

Approach: The literature (1976–2000) was searched using MEDLINE and Knowledge Server with “alcohol and CDT” as the search items. The data were reviewed systematically, checked for redundancy, and organized in sequence based on the steps involved in CDT analysis.

Content: The review is divided into sections based on microheterogeneity of human serum transferrin (Tf), definition of CDT, structure of human serum CDT, pathomechanisms of ethanol-induced CDT increase, preanalysis, analysis, and medical interpretation (postanalysis). Test-specific cutoff values for serum CDT and causes of false positives and negatives for chronic alcohol abuse are discussed and summarized.

Summary: Asialo- and disialo-Fe2-Tf, which lack one or two complete N-glycans, and monosialo-Fe2-Tf (structure remains unclear) are collectively referred to as CDT. Diminished mRNA concentration and glycoprotein glycosyltransferase activities involved in Tf N-glycan synthesis and increased sialidase activity most likely account for alcohol-induced increases in CDT. Knowledge about in vivo and in vitro effects on serum CDT is poor. Reliable CDT and non-CDT fractionation is needed for CDT measurement. Analysis methods with different analytical specificities and recoveries decreased the comparability of values and statistical parameters of the diagnostic efficiency of CDT. CDT is the most specific marker of chronic alcohol abuse to date. Efforts should concentrate on the pathomechanisms (in vivo), preanalysis, and standardization of CDT analysis.

Glycosylation of transferrin in Alzheimer's disease and alcohol-induced dementia

Transferrin is a glycosylated metal-binding serum protein. Carbohydrate-deficient transferrin (CDT) is a marker of recent and heavy alcohol intake. A genetic variant of transferrin, TfC2, occurs with increased frequency in patients with Alzheimer's disease (AD). Hence the question arose whether, in addition to an altered amino acid sequence, there could also be a difference in the glycosylation state of transferrin in patients with dementia. Serum samples of 37 AD and 13 Alcohol-induced dementia patients as well as 10 healthy controls were analyzed for abnormal Tf variants, using isoelectric focusing followed by blotting with anti-Tf antibodies. This allowed the direct visualization of glycosylation variants of transferrin, and assessment of any increase in underglycosylated forms (di-, mono- and asialo transferrin).