Volume 4 Issue 4 April, 2014
Consultation Liaison Psychiatry Focus: ‘Pathology’
It is well known that alcohol negatively affects the physical, mental & social health of mankind. It is associated with
increased morbidity and about 2.5 million die each year due to it. Diseases involving liver, heart, kidney and even many
malignancies are directly or indirectly found associated with its excessive use.
So, early diagnosis of & intervention in alcohol use disorder is very important. Alcohol abuse & dependence can be
diagnosed based on clinical background & questionnaire (WHO ICD10 or DSM 5 criteria). On the other hand laboratory investigations provide objective information on the extent of problem with estimation of Glutamyl Transferase (GGT), MCV, SGPT, CDT etc. Carbohydrate Deficient Transferrin (CDT) is considered most specific marker of chronic alcohol abuse to date. CDT estimation was first reported in 1976 by Stibler and Kjellin in cerebro spinal fluid and later in serum. Elevation of both GGT & CDT is considered as marker for chronic alcoholism while only CDT elevation is inconclusive. Sensitivity of CDT is almost similar to that of GGT but is more sensitive than other biomarkers, like – MCV, Aspartate transaminase, and Alanine transaminase. However specificity is more in CDT than in GGT (92% vs. 75%) . A reference value for CDT has been advised as follows:
| Negative | In conclusive | Positive |
| <1.3 | > 1.3 – <1.7 | > 1.7 |
Transferrin is the most important iron transporter in blood. It is synthesized mainly in hepatocytes and consists of three
sub structural domains: a single polypeptide chain, two independent metal ion-binding sites. Normally transferrin
molecule possesses 3 to 5 sialic acid residues as side chains. On the basis of the degree of sialylation there are various
isoforms of transferrin. In persons abusing alcohol there is significant increase in transferrins with fewer or no sialic acid
residues. CDT are the least sialylated isoforms of Transferrin – with 0 (asialo), 1 (monosialo), and 2 (disialo) sialic acids.
The pathomechanisms for increase of CDT isoforms in chronic alcoholism are not completely understood at present. It is most likely that ethanol and/or its metabolite acetaldehyde affect N-glycan chain synthesis in the Golgi apparatus.
Diminished activities of galactosyltransferase and N-acetylglucosaminyltransferase results in less sialysation of transferrin.
METHOD:
Initially isoelectric focusing separation and immunoassay assay were the methods for CDT estimation. But
now better assay methods are available. It includes microcolumn chromatography separation assays that measure CDT.
In normal subjects CDT comprises less than 1.7 % of total transferrin concentration. CDT level is related to prolonged
consumption of large quantities of alcohol. More than 60 g of alcohol / day over at least a week raises the level of CDT. A single episode of heavy drinking does not elevate CDT. 95 % of the individuals with no or normal drinking habit shows < 1.7 % CDT. CDT has a long half-life of 15 days. Therefore even after complete alcohol absenteeism it takes 1 to 2 months for CDT to revert to normal levels.
Dr. J R Prasad DCP, MD. Dept. of Pathology, Patliputra Medical College (PMC), Dhanbad
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