Alcohol dependence: is carbohydrate-deficient transferrin a marker for alcohol intake?

The carbohydrate-deficient transferrin test in hospital practice

We report an experience in two hospital populations of the use of a commercially available kit for the detection of carbohydrate-deficient transferrin (CDT). Patients from a drug and alcohol unit and a gastroenterology clinic at two hospitals were selected for the study. Sera were used from blood samples collected for routine biochemical assays. All patients had a specific alcohol history taken by one clinician and CDT results were correlated with reported alcohol intake by the patient and where relevant by their relatives. Sensitivity and specificity of the CDT assay were calculated using an alcohol intake of 60 g/day as the cut-off point for detection of heavy drinking. The CDT assay had a specificity of 95%; a sensitivity of 80% and a 90% positive and 89% negative predictive value. The severity and type of liver disease had little influence on the CDT result and a high alcohol intake was the only predictor of a raised CDT concentration. The assay provided information not available from routine investigations in some patients and also proved useful in monitoring patients over periods of up to 4 years. The test has a role in the evaluation of patients in a hospital practice where routine histories of alcohol intake may lack sensitivity and where other diseases may cause routine liver tests to be unreliable.

Exclusion of trisialo-transferrin from carbohydrate-deficient transferrin measurement: advantage in patients with chronic liver disease?

BACKGROUND

Biological markers for chronic alcohol consumption like MCV or gammaGT or carbohydrate deficient transferrin (CDT) are useful, but far from being perfect. In patients with liver disease a reliable marker for chronic alcohol consumption as the underlying etiology is highly needed. Recently, a new ELISA based version of the carbohydrate-deficient-transferrin (CDT-TRISIALO (-)) assay has been developed, which measures asialo-, monosialo- and disialo transferrin, but excludes trisialo- transferrin; that modification suggests higher sensitivity and specificity in detecting recent alcohol consumption in patients.

AIMS

The study goal was to evaluate the sensitivity, specificity, positive and negative predicitive value of this new carbohydrate-deficient-transferrin assay (CDT-TRISIALO (-)) in a group of patients with liver disease and to compare the results with that of the established CDT assay (CDT-TRISIALO (+)).

PATIENTS AND METHODS

Our study population consisted of 110 consecutive patients (male: n = 80 [72.7 %], female: n = 30 [27.3 %]) with liver disease of the following etiologies: chronic alcohol consumption (n = 51 [46.4 %]; Out of them 30 alcohol abusing patients were assessed by cage = 1 and 21 alcohol dependent patients were assessed by cage = 2, chronic viral hepatitis (n = 33 [30.0 %]) including 25 [22.7 %] patients with chronic hepatitis C infection and 8 [7.3 %] patients with chronic hepatitis B infection), haemochromatosis (n = 4 [3.6 %]), mechanical cholestasis (n = 17 [15.5 %]) and other liver diseases (n = 5 [4.6 %] including autoimmune hepatitis (n = 2) and primary biliary cirrhosis (n = 3)). 27.3 % of our patients (n = 30) had no liver cirrhosis whereas the majority (72.7 %, n = 80) had liver cirrhosis.

RESULTS

In our population of liver disease patients the CDT-TRISIALO (-) assay had a sensitivity of 72.7 % and specificity of 58.1 % for recent alcohol consumption at the published cutoff level of 2.6 %. The positive predictive value was 34.0 % and the negative predictive value was 87.8 %. Sensitivity and specificity of the CDT-TRISIALO (+) assay at the recommended cutoff level of 4.7 % were similar, 77.3 % and 49.3 %, respectively. The positive and negative predictive values were 30.9 % and 88.1 %. CDTTRISIALO (+) and CDT-TRISIALO (-) levels increased significantly with higher Child-Pugh stages.

CONCLUSION

The newly developed carbohydrate deficient transferrin test (CDT-TRISIALO (-)) is of no advantage as compared to the established assay (CDT-TRISIALO (+)) when used in a patient population with liver disease. In that population, normal CDT-TRISIALO (-) helps to exclude recent alcohol consumption; this results from the high negative predictive value of a normal CDT-TRISIALO (-).

The analysis of carbohydrate-deficient transferrin, marker of chronic alcoholism, using capillary electrophoresis

Carbohydrate-deficient transferrin (CDT) is currently considered to be the best available marker for the diagnosis of chronic alcoholism. A large variety of methods have been developed, demonstrating the need for standardisation. Commercially available anion-exchange chromatographic-based assays are easy to use and require no specialised, expensive instruments. However, these methods cannot identify genetic transferrin variants or the carbohydrate-deficient glycoprotein syndrome. In 1989, a capillary isoelectric focusing method was developed for quantitative measurement of CDT. Despite the optimal resolution, this method is not easily applied in a clinical routine environment due to the complexity of analysis. Capillary electrophoresis in a polymer network using coated capillaries allowed full resolution of the sialoforms of human transferrin. The drawbacks due to an expensive and time-consuming sample preparation were eliminated when a method in neat serum was developed. Capillary zone electrophoresis allowed full resolution of the transferrin isoforms with a high analytical performance in a short analysis time thanks to a strong electroosmotic flow. Genetic transferrin variants were easily detected, avoiding false-positive results. Also, using capillary zone electrophoresis, it was shown that CDT is a suitable marker of chronic alcohol abuse detection in transferrin CD (common/cathodal) variants.

Sensitivity and specificity of carbohydrate-deficient transferrin in drinking experiments and different patients

Information provided by patients about the amounts of alcohol they drink may often be too subjective and therefore unreliable. Because of the possible serious consequences of interactions between alcohol and medication, reliable laboratory test markers for alcohol consumption are needed. Carbohydrate-deficient transferrin (CDT) is at present the best available objective measure of drinking behavior. During a withdrawal trial, 92 alcohol-dependent patients who had been admitted to a hospital in an ethanol-intoxicated state were monitored over the following 28 days by using the percent carbohydrate-deficient transferrin (%CDT of total transferrin) (%CDT) method. At the time of admission, 63% showed elevated %CDT levels. After a subsequent period of abstinence, a decrease in %CDT levels was apparent in four different groups of patients, whereas in two groups, comprising the greatest number of patients, normal %CDT levels were evident after 14 days of abstinence. In patients whose CDT levels were very high at study initiation, it took at least 21 to 28 days--and sometimes longer--for CDT to decrease to the radioimmunoassay (RIA) %CDT test cutoff point of 2.5. In a further study of 56 male alcohol-dependent patients, we measured liver enzyme concentrations, mean corpuscular volume (MCV), and four CDT variants on the first day of evidence of withdrawal syndrome. We found a significant correlation between results on the Munich Alcoholism Test (MALT) and MCV levels; among gamma-glutamyltransferase (GGT), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels; and among all four CDT variants. A cluster analysis yielded three clusters: (1) GGT, AST, and ALT levels; (2) MCV levels and MALT results; and (3) all CDT measurement variants. We conclude that these three clusters measure different detriments to the patient and that all available CDT variants are commensurate.

Plasma sialic-acid index of apolipoprotein J (SIJ): a new alcohol intake marker

Although plasma carbohydrate-deficient transferrin (CDT) is considered a viable biochemical marker for chronic alcohol consumption, it is valid only when an individual's daily alcohol consumption exceeds 60 g. In addition, it is less sensitive in women drinkers than in men drinkers. We have established that chronic alcohol consumption impairs the hepatic sialylation of a number of glycoproteins by specifically down-regulating Gal-beta-1,4GlcNAc alpha2,6-sialyltransferase mRNA. Significantly, we found that chronic ethanol consumption markedly inhibits hepatic sialylation of apolipoprotein J (Apo J), a 70-kDa N-glycosylated protein of plasma HDL. Because the sialic-acid index of Apo J (SIJ; moles of sialic acid per mole of Apo J protein) is approximately seven times more than that for transferrin (28 vs. 4), we have evaluated whether plasma SIJ would be an even more sensitive marker for chronic ethanol consumption than CDT in both rats and human subjects. The method involves immunoaffinity purification of plasma HDL-Apo J, followed by its sialic acid determination. We have found that chronic ethanol feeding resulted in loss of sialic acid residues of plasma HDL-Apo J in rats. This loss of sialic acid was positively correlated with both amount and duration of ethanol treatment. In human subjects, an intake of about 60 g of alcohol for 30 days led to almost 50% (P <.01) depletion of sialic acid from plasma HDL-Apo J. Further, we established that there was a positive correlation of alteration in SIJ with alcohol consumption, detoxification, abstinence, and relapse in human alcohol-dependent patients (sensitivity, 90%-92%). In addition, plasma SIJ was decreased by 50%-57% (P <.01) in both male and female alcohol-dependent subjects. We suggest that plasma SIJ can be used as a viable marker for early detection of chronic alcohol consumption in human beings.

Determination of Carbohydrate-deficient Transferrin Using Capillary Zone Electrophoresis

Background: Current methods for carbohydrate-deficient transferrin (CDT) often suffer from low precision, complexity, or risk of false positives attributable to genetic variants. In this study, a new capillary zone electrophoresis (CZE) method for CDT was developed.

Methods: CZE was performed on a P/ACE 5000 using fused-silica capillaries [50 μm (i.d.) × 47 cm] and the CEOFIX CDT buffer system with addition of 50 μL of anti-C3c and 10 μL of anti-hemoglobin. Native sera were loaded by high-pressure injection for 3 s, separated at 28 kV over 12 min, and monitored at 214 nm.

Results: CDT was completely resolved by differences in migration times (di-trisialotransferrin, 9.86 ± 0.05 min; monosialotransferrin, 9.72 ± 0.05 min; asialotransferrin, 9.52 ± 0.04 min), with a CV of 0.15%. The number of theoretical plates was 312 000 ± 21 000 for the mono- and 199 000 ± 6500 for the di-trisialylated transferrin. Genetic CB and CD variants showed prominent peaks with migration times of 10.12 ± 0.06 and 9.89 ± 0.03 min, respectively, and the carbohydrate-deficient glycoprotein syndrome could be detected, excluding false-positive results. CZE results (as a percentage; y) correlated with the Axis %CDT TIATM (x) values by Deming regression analysis: y = 1.92x − 7.29; r = 0.89. CDT values in 130 healthy nonalcoholics were determined. The 2.5th and 97.5th percentiles were 1.84% and 6.79%.

Conclusions: CZE without sample pretreatment can determine CDT with good precision, allows detection of variants, and correlates with ion-exchange chromatography.

Normalization rate and cellular localization of phosphatidylethanol in whole blood from chronic alcoholics

Phosphatidylethanol (PEth) is an abnormal phospholipid which is formed in the presence of ethanol, via the action of phospholipase D (PLD). PEth in blood is a potential marker of alcohol abuse. The present study was made to determine the compartmentalization and the elimination rate of PEth in human whole blood. PEth was assayed by an improved HPLC technique, with evaporative light-scattering detection. Blood from six alcoholic males was separated into different blood cell fractions. The PEth concentration in whole blood was 2.5+/-0.9 and 1.9+/-1.1 micromol/l in erythrocytes. Only one subject had detectable PEth in the mononuclear cells. Fifteen patients (13 men, two women) with chronic alcoholism, were followed as inpatients, after admission to an alcohol detoxification clinic. PEth, carbohydrate-deficient transferrin (CDT) and gamma-glutamyltransferase (GGT) were measured on days 1, 3, 5 and 7 after admission. Linear regression analysis of logarithmic PEth values in individuals, with measurable PEth at day 1, gave a good fit (P<0.001) with the one-compartment elimination model. The half-life was calculated as 4.0+/-0.7 days. A weak significance (P<0.05) was observed in the correlation of PEth at day 1 and half-life values of the same subjects.

Carbohydrate-deficient transferrin as compared to other markers of alcoholism: a systematic review

This is a systematic review of the studies in which carbohydrate-deficient transferrin (CDT) has been compared to other laboratory markers in different experimental conditions, clinical settings, and populations. Only the studies (n = 54) in which CDT was compared either to the conventional or new biological markers of alcoholism, heavy drinking, or alcohol use were selected for further evaluation. Two prospective studies indicate that in men CDT is slightly more sensitive than gamma-GT in reflecting changes in these markers caused by drinking of a moderate and fixed amount of alcohol during three to four weeks. In one prospective study, in which the drinking history of male heavy drinking volunteers was as close the golden standard as possible; that is, obtained by a prospective anonymous drinking diary, CDT was slightly but not significantly better marker than conventional laboratory markers (ASAT, ALAT, gamma-GT and beta-Hex) in the identification of men drinking more than 400 g of alcohol daily. Similar prospective studies concerning women have not been done. Six prospective treatment outcome studies indicate that CDT may be a significantly more sensitive marker than gamma-glutamyltransferase (gamma-GT) in the detection of relapses in male alcoholics. However, these two tests can also be considered to be complementary markers. Furthermore, in the detection of relapses the baseline values of CDT and gamma-GT should be measured and compared on individual basis to the pretreatment values. Comparable data are not available from female alcoholics. In selective materials comprising male alcoholics and heavy drinkers, CDT was found to be a slightly more sensitive marker than gamma-GT in seven retrospective studies. In five studies, gamma-GT was slightly better. However, the differences between CDT and gamma-GT in general were not statistically significant. In three studies, the combined use of CDT and gamma-GT improved the sensitivity but with the expense of specificity. Only four studies included women and in three of these the sensitivity of gamma-GT was better than that of CDT, whereas in one study CDT was better than gamma-GT in the detection of female heavy drinkers. Seven studies performed in primary health care settings and among young populations demonstrate that the performance of CDT in the identification of heavy and problem drinkers in this type of populations is very low, although comparable to the poor performance of the conventional laboratory markers, too. According to seven studies, the sensitivity of gamma-GT is slightly better than that of CDT in the identification of excessive alcohol consumption among hospitalized male and female patients. However, in this type of hospital setting, the specificity of CDT is markedly higher than that of gamma-GT. There is some evidence indicating that the performance of the tests can be improved with the combined use of both tests. Eight studies indicate that both in men and women CDT is a better marker than gamma-GT in the identification of alcohol abuse among patients with alcoholic and nonalcoholic liver diseases. This is mostly due to the higher specificity of CDT as compared to that of gamma-GT.

Carbohydrate-deficient transferrin in the assessment of harmful alcohol consumption: diagnostic performance and clinical significance

The last decade saw the emergence of carbohydrate-deficient transferrin (CDT) as the most promising marker for the diagnosis of alcohol abuse. Daily alcohol consumption of four beers, four glasses of wine or three standard drinks causes increased concentrations of CDT in serum. CDT is serum transferrin with a reduced content of oligosaccharides due to the detrimental effects of alcohol metabolism on the glycosylation pathway of hepatocytes and/or the increased activity of circulating glycosidases in serum. Most current CDT procedures entail separation of normal transferrin from CDT in a charged matrix-like isoelectric focusing and ion exchange chromatography, followed by detection/quantitation of CDT by a myriad of immunoassays: immunoblotting, radioimmunoassay, enzyme immunoassay and nephelometry. New CDT procedures present the advantages of improved performance, inexpensive automation and CDT results expressed as a percentage of total serum transferrin. CDT's major asset is its high specificity in well-defined populations i.e. individuals ingesting 60 g alcohol daily for at least a week.The sensitivity rates, which vary between 22% and 81%, depend on the amount of alcohol ingested, time of sample collection after the cessation of drinking, age, gender and the cut-off point chosen for analysis of tests' results. Regarding clinical applications, best outcome is achieved when the test is used to confirm a suspicion of alcohol abuse and when monitoring abstinence and relapses.The low prevalence of alcohol abuse in the general population challenges its use as a screening test.With the advent of inexpensive automation and the constant emergence of innovative, improved tests, we are seeing the rise of a new era in alcohol abuse diagnosis as affordability and education allows widespread use of CDT in a variety of settings.

The ratio of aspartate aminotransferase to alanine aminotransferase: potential value in differentiating nonalcoholic steatohepatitis from alcoholic liver disease

OBJECTIVE

The ratio of aspartate aminotransferase (AST) to alanine aminotransferase (ALT) is often greater than 2:1 in alcoholic hepatitis. The purpose of this study was to determine whether this ratio may be used to distinguish nonalcoholic steatohepatitis (NASH) from alcoholic liver disease.

METHODS

Patients with NASH were matched with controls with alcoholic liver disease based on age, gender, and date of diagnosis. The diagnosis of alcoholic liver disease was based on exclusion of other causes and a significant history of alcohol consumption. The diagnosis of nonalcoholic steatohepatitis was based on exclusion of other causes of liver disease and a liver biopsy showing > 10% steatosis and inflammation. The two sided Student t test was used for statistical analysis.

RESULTS

From 1990 to 1996, 70 patients with NASH were matched with 70 subjects with alcoholic liver disease. Patients with NASH had a mean AST to ALT ratio of 0.9 (range 0.3-2.8, median 0.7) and subjects with alcoholic liver disease a mean ratio of 2.6 (range 1.1-11.2, median 2.0). The mean AST levels were 66 U/L and 152 U/L, and the mean ALT levels 91 U/L and 70 U/L, in the nonalcoholic steatohepatitis and alcoholic liver disease groups, respectively. Although the absolute aminotransferase levels were significantly different in the two groups (p < 0.05), the greatest difference was observed in the AST to ALT ratio (p < 0.000001). Subset analysis of patients with NASH revealed mean AST to ALT ratios of 0.7, 0.9, and 1.4 for subjects with no fibrosis, mild fibrosis, or cirrhosis, respectively. The differences among these ratios were statistically significant (p < 0.05).

CONCLUSIONS

The AST to ALT ratio appears to be a useful index for distinguishing nonalcoholic steatohepatitis from alcoholic liver disease. Although values < 1 suggest NASH, a ratio of > or = 2 is strongly suggestive of alcoholic liver disease.