The Specificity of the CDT Assay in General Practice: The Influence of Common Chronic Diseases and Medication on the Serum CDT Concentration

Biochemical alcohol screening in primary health care

Alcohol biomarkers such as carbohydrate-deficient transferrin (CDT) and gamma-glutamyltransferase (GGT) have significant potential for enhancing the quality of medical treatment in primary health care settings. Recent studies demonstrate that these laboratory tests can help the general practitioner in several ways. First, CDT and GGT can detect current heavy drinking in primary care patients with a fair degree of sensitivity (approximately 60% to 70%), with CDT being more specific (approximately 90%). When combined with self-report tests, they can provide a clinically useful alcohol screening battery. Second, elevated CDT and GGT levels have been correlated with specific alcohol-sensitive diseases (e.g., hypertension) and, as such, can serve as risk indicators for those diseases. Third, alcohol biomarkers have proven to be useful in monitoring the effectiveness of brief alcohol interventions with medical patients. Unfortunately, preliminary findings indicate that physicians have little knowledge of current biomarker research as applied to primary health care. Translational studies are needed on methods to facilitate knowledge and use of alcohol biomarkers by general practitioners.

Carbohydrate-deficient transferrin for detection and monitoring of sustained heavy drinking. What have we learned? Where do we go from here?

Carbohydrate-deficient transferrin (CDT) has been widely investigated as a biological marker of heavy alcohol consumption. In general, it has been found to be at least as sensitive and probably more specific than gamma-glutamyltransferase (GGT). Because the two analytes are not highly correlated, their use in parallel enhances the sensitivity of detection of heavy alcohol consumption, especially in clinical populations. Women as a group produce more CDT under natural conditions and may produce less CDT in response to heavy drinking. Carbohydrate-deficient transferrin has found a place in the monitoring of alcoholics during treatment. Changes in CDT levels from individualized baseline values seem to be more sensitive to lower level relapse drinking than is the use of raw cut-off values. There are some conditions such as severe liver disease in which higher than normal levels of CDT are produced, thereby reducing the specificity of this marker for detecting heavy drinking under certain conditions. Future directions for the use of CDT include standardization and automation of measurement technology, evaluation of how to use it wisely in myriad medical and institutional settings, understanding more thoroughly the gender issues in its production, and greater evaluation of its performance as a monitoring tool during treatment and follow-up situations. How to combine CDT with both verbal tools of alcohol assessment and newer biological markers will also need more extensive evaluation.