Carbohydrate-deficient transferrin (CDT, also known as desialotransferrin or asialotransferrin) is a laboratory test used to help detect heavy

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

consumption.

Physiology

Transferrin Transferrins are glycoproteins found in vertebrates which bind to and consequently mediate the transport of iron (Fe) through blood plasma. They are produced in the liver and contain binding sites for two Fe3+ ions. Human transferrin is encode ...

is a serum protein that carries iron through the bloodstream to the bone marrow, where red blood cells are manufactured, as well as to the liver and spleen. Structurally, transferrin is a polypeptide with two ''N''-linked polysaccharide chains. These polysaccharide chains are branched with sialic acid residues. Sialic acid is a monosaccharide

carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or m ...

. Various forms of transferrin exist, with differing levels of sialylation. The most common form is tetrasialotransferrin, with four sialic acid chains. In persons who consume significant quantities of alcohol (usually more than 4 or 5 alcoholic beverages a day for two weeks or more) , the proportion of transferrin with zero, one, or two sialic acid chains is increased. These are referred to as ''carbohydrate-deficient transferrins''. These carbohydrate-deficient transferrins can be measured in the bloodstream, and are important markers for alcohol use disorder.

Test for alcohol consumption

Carbohydrate-deficient transferrin is elevated in the blood of people with heavy alcohol consumption but elevated levels can also be found in a number of medical conditions. The limitations of the assay depend upon the methodology of the test. HPLC (High Performance Liquid Chromatography) can detect certain genetic variants and potential liver diseases affecting CDT. Used with other tests, such as

gamma glutamyl transferase Gamma-glutamyltransferase (also γ-glutamyltransferase, GGT, gamma-GT, gamma-glutamyl transpeptidase; ) is a transferase (a type of enzyme) that catalyzes the transfer of gamma- glutamyl functional groups from molecules such as glutathione t ...

(GGT),

aspartate aminotransferase Aspartate transaminase (AST) or aspartate aminotransferase, also known as AspAT/ASAT/AAT or (serum) glutamic oxaloacetic transaminase (GOT, SGOT), is a pyridoxal phosphate (PLP)-dependent transaminase enzyme () that was first described by Arthur ...

(AST), and

alanine aminotransferase Alanine transaminase (ALT) is a transaminase enzyme (). It is also called alanine aminotransferase (ALT or ALAT) and was formerly called serum glutamate-pyruvate transaminase or serum glutamic-pyruvic transaminase (SGPT) and was first character ...

(ALT), carbohydrate-deficient transferrin can be a useful tool in identifying problem drinking, such as alcohol use disorder. However, it is less sensitive than

phosphatidylethanol Phosphatidylethanols (PEth) are a group of phospholipids formed only in the presence of ethanol via the action of phospholipase D (PLD). The lipid accumulates in the human body and competes at agonists sites of lipid-gated ion channels contributing ...

(PEth) in detecting current regular alcohol consumption. The ethanol conjugates

ethyl glucuronide Ethyl glucuronide (EtG) is a metabolite of ethanol which is formed in the body by glucuronidation following exposure to ethanol, usually from drinking alcoholic beverages. It is used as a biomarker to test for ethanol use and to monitor alcohol ab ...

and

ethyl sulfate Ethyl sulfate (IUPAC name: ethyl hydrogen sulfate), also known as sulfovinic acid, is an organic chemical compound used as an intermediate in the production of ethanol from ethylene. It is the ethyl ester of sulfuric acid. History This substance ...

remain positive for up to three days after ethanol consumption and are quite useful for detection of occult/denied alcohol use disorder. Both these substances are detectable clinically through urine drug testing by commercial toxicology labs. CDT is measured by taking a sample of a patient's blood. Apparently healthy individuals with no or low reported alcohol consumption and a negative

Alcohol Use Disorders Identification Test The Alcohol Use Disorders Identification Test (AUDIT) is a ten-item questionnaire approved by the World Health Organization to screen patients for hazardous (risky) and harmful alcohol consumption. It was developed from a WHO multi-country collab ...

(AUDIT) will have a %CDT <1.7% (95th percentile for the social drinking population). Elevated levels of CDT suggest recent heavy alcohol consumption, especially if other liver-associated enzymes (such as GGT) are elevated. Although recent heavy alcohol use is most commonly associated with elevated CDT, certain rare liver disorders can also increase levels of CDT. CDT levels are less useful for detecting alcohol use disorder in people with other liver diseases.

References

{{reflist Chemical pathology Transferrins