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

Monitoring of transferrin isoforms in biological samples by capillary electrophoresis

Work dealing with the monitoring of transferrin isoforms in human serum and other body fluids by capillary electrophoresis is reviewed. It comprises capillary zone electrophoresis and capillary isoelectric focusing efforts that led to the exploration and use of assays for the determination of carbohydrate-deficient transferrin as a marker for excessive alcohol intake, genetic variants of transferrin, congenital disorders of glycosylation and β-2-transferrin, which is a marker for cerebrospinal fluid leakage. This paper provides insight into the development, specifications, strengths, weaknesses, and routine use of the currently known capillary electrophoresis based assays suitable to detect transferrin isoforms in body fluids. The achievements reached so far indicate that capillary zone electrophoresis is an attractive technology to monitor the molecular forms of transferrin in biological specimens as the assays do not require an elaborate sample pretreatment and thus can be fully automated for high-throughput analyses on multicapillary instruments. Assays based on capillary isoelectric focusing are less attractive. They require immunoextraction of transferrin from the biological matrix and mobilization after focusing if instrumentation with a whole-column imaging detector is not available. Interactions of the carrier ampholytes with the iron of transferrin may prevent iron saturation and thus provide more complicated isoform patterns.

Comparative evaluation of capillary zone electrophoresis and HPLC in the determination of carbohydrate-deficient transferrin

BACKGROUND

Transferrin (Tf) glycoform lacking one or two complete or incomplete glycan chains (i.e., asialo-monosialo- and disialo-Tf) typically appear in blood after chronic alcohol consumption, though recently it was reported that monosialo-Tf is associated with trisialo-Tf but not with alcohol consumption. These glycoforms are collectively known as carbohydrate-deficient transferrin (CDT). Since samples from alcoholic patients are characterized by decreased sialic acid content in serum transferrin, the assessment of CDT is thereby widely used for laboratory evaluation of chronic alcohol abuse.

METHODS

CDT analysis has been performed in 6011 consecutive subjects undergoing national mandatory testing after the confiscation of driving license for driving under the influence of alcohol. Out of the 6011 specimens, 539 (9%) displayed values exceeding the specific cut-off (>1.3%) on multicapillary electrophoresis (MCE) (Capillarys2 Sebia, France), and were further analyzed with a routine high-pressure liquid chromatography (HPLC) technique.

RESULTS

The overall correlation between the methods in the total 539 samples was satisfactory, displaying a correlation coefficient (r) of 0.960. Nevertheless, the correlation was lower in the group with CDT values comprised between 1.3% and 1.9% (group 1; r=0.60) than in those with CDT values >2.0% (group 2; r=0.98). Moreover, the discordance between values exceeding the method-specific threshold in the former group of samples was also remarkably high (62% of samples in group 1 vs. 0.6% in group 2). Finally, a significant difference of CDT values was observed in group 1 (p<0.001), and in group 2 (p<0.0001) by Wilcoxon test.

CONCLUSIONS

The MCE is characterized by a high throughput and it seems a suitable approach for laboratory monitoring of alcohol abuse when CDT is used as medical parameter in the diagnosis and follow-up of heavy drinking. However, CDT measured by screening techniques must be confirmed by a confirmatory technique, in particular for forensic purpose.

gamma-glutamyltransferase and pathogenesis of cardiovascular diseases

Cardiovascular epidemiology has recently highlighted a clear link between serum gamma-glutamyltransferase (GGT) and risk for stroke, infarction and cardiovascular death, associated with the evolution of atherosclerosis-related conditions, such as coronary artery and cerebrovascular disease. Thus, serum GGT is now recognized as a cardiovascular prognostic marker. However, the reasons for the association between serum GGT elevations and unfavorable prognosis remain to be defined. Histochemistry and biochemistry have provided intriguing clues, focusing new research approaches on the complex issue of monitoring and treatment of chronic cardiovascular conditions.

Carbohydrate‐deficient transferrin determined in blood microsamples from healthy newborns by using capillary zone electrophoresis

OBJECTIVE

There is a paucity of studies on quantitative determination of carbohydrate-deficient transferrin (CDT) in newborns. The aim of our study was therefore to determine CDT concentrations in newborns by using capillary zone electrophoresis (CZE).

MATERIAL AND METHODS

Capillary blood was collected from the heels of 28 at-term healthy newborns, simultaneously with the Guthrie card screening. Forty-seven adults were examined as controls. CZE separations were performed with a P/ACE MDQ capillary electropherograph in uncoated fused-silica capillaries using a commercial reagent kit. After iron saturation, the samples were loaded by application of 0.5 psi for 15 s, and separated under 28kV with UV detection. All relevant transferrin (Tf) glycoforms were separated within 7 min. CDT quantification (%CDT) was carried out by calculating the percentage ratio between the sum of the peak areas of CDT-related glycoforms and the sum of peak areas of all Tf glycoforms.

RESULTS

In most cases, good separations of Tf glycoforms were obtained. In the newborns the %CDT was 0.51 versus 0.66 in adults (difference not statistically significant). Trisialo-Tf concentration was significantly lower in newborns (3.20) than in adults (4.11). Furthermore, pentasialo-Tf appeared to be lower in newborns (7.30) than in adults (14.00), but because complete separation of the peaks of tetrasialo- and pentasialo-Tf was not always possible, this finding could not be confirmed statistically.

CONCLUSIONS

CZE showed definite advantages in terms of volume of blood to be collected, simplicity and standardization of analysis and, because of the direct detection of the separated zones, accuracy of quantification. The present study provides the basic information in the search for glycosylation defects in newborns.

Validation study of Axis-Shield carbohydrate-deficient transferrin (CDT) on ARCHITECT chemistry analyzer

BACKGROUND

Carbohydrate-deficient transferrin (CDT) is a biochemical marker used for identifying chronic alcohol intake. We developed and validated an ARCHITECT c8000 (Abbott) instrument application for the Axis-Shield %CDT immunoassay.

METHODS

Standard CLSI (Clinical and Laboratory Standards Institute) evaluation protocols were performed.

RESULTS

The Axis-Shield %CDT ARCHITECT method was standardized against the Axis-Shield %CDT microtiter test by linear regression analysis (n=50 mean of duplicate, R=0.996). Method comparison by Deming regression revealed a slope of 1.01 and an intercept of -0.03 with Axis-Shield %CDT microtiter test (n=50 in duplicate, R=0.995), and a slope of 0.82 and an intercept of 1.09 with HPLC method (n=47 in duplicate, R=0.990) as the candidate IFCC (International Federation of Clinical Chemistry and Laboratory Medicine) reference method. The predicted medical decision points (MDPs) are both 2.6% and equal the MDP that is generally used for the Axis-Shield %CDT tests. Precision derived from pooled patient sera (low level) and commercially available control material (high level) was excellent. Total variation was 3.2% and 1.8%, respectively.

CONCLUSIONS

The Axis-Shield %CDT ARCHITECT method, as one of the first Axis-Shield applications on a large-scale analyzer, is a reliable test for routine %CDT analysis providing precise and well-standardized %CDT results.

Characterization of transferrin glycoforms in human serum by CE-UV and CE-ESI-MS

Human transferrin (Tf) is a model glycoprotein for congenital disorders of glycosylation (CDG) diagnosis. In the last few years, new CE-UV methods for intact Tf glycoforms analysis have been developed using nonvolatile BGEs and organic modifiers. However, the use of these BGEs does not allow the coupling of these procedures with electrospray MS (ESI-MS). In this study, a new CE-UV separation method of Tf glycoforms is developed, using a double-layer stable coating and a volatile BGE based on ammonium acetate. The separation method is optimized using standard Tf and their potential is demonstrated applying the method to the analysis of sera Tf from healthy individuals and CDG patients. The CE-UV separation method has been coupled to ESI-MS detection. Main parameters such as sheath liquid composition are optimized in order to obtain a good sensitivity. The CE-ESI-MS method has also been used in serum samples obtaining the separation of the different proteins present in serum and partial separation of Tf glycoforms. Different mass spectra and deconvoluted molecular masses were obtained for each sialoform, allowing unequivocal glycoform identification.

Recent advances in capillary electrophoresis for biomarker discovery

The use of non-invasive methods for detecting biomarkers opens a new era in patient care, since clinical investigators have long been searching for accurate and reproducible measurements of putative biomarkers. There are many factors which make this research challenging, beginning with lack of standardization of sample collection and continuing through the entire analytical procedure. Among the variety of methods so far used for biomarker screening, capillary electrophoresis represents a robust, reliable, and widely used analytical tool. This review will focus on recent applications of CE to the analysis of body fluids and tissues for identification of biomarkers.

Carbohydrate-deficient transferrin (CDT) as a marker of alcohol abuse: a critical review of the literature 2001-2005

The diagnosis of alcohol abuse based on objective data is a necessary requirement in both clinical and forensic environments. Among the different biomarkers of chronic alcohol abuse, carbohydrate-deficient transferrin (CDT) is world wide recognized as the most reliable indicator. However, several problems about the real meaning of CDT and the reliability of its use for the diagnosis of alcohol abuses are still open, as reported by numerous research articles and reviews. The present article presents a critical review of the literature on CDT appeared in the period from 2001 to 2005 (included). The article is organized in the following sections: (1) introduction, (2) definition and structure of human serum CDT, (3) pathomechanisms of the ethanol-induced CDT increase, (4) preanalysis, (5) analysis, (6) data interpretation, (7) review papers, (8) conclusions. As many as 127 papers appeared in the international literature and retrieved by the search engines PubMed and Scopus are quoted.

Primary biliary cirrhosis is not a clinical condition for increased carbohydrate-deficient transferrin: experience with four independent CDT analysis methods

BACKGROUND

Primary biliary cirrhosis (PBC) is considered as an important cause for increased carbohydrate-deficient transferrin (CDT). The underlying pathomechanism is difficult to explain by the pathogenesis and/or consequences of PBC. We tested whether PBC causes increased CDT results with current CDT analysis methods and, if so, whether this depends on the CDT analysis principle.

METHODS

48 serum samples from PBC patients were analyzed by HPLC, microcolumn CDT and non-CDT fractionation followed by a turbidimetric immunoassay, particle-enhanced immunonephelometry with monoclonal CDT antibodies, and capillary electrophoresis. The test-specific decision limits were used for categorization of the CDT analysis results into normal and increased values.

RESULTS

HPLC: 47 normal/1 increased, microcolumn+TIA: 46 normal/2 increased, particle-enhanced immunonephelometry: 41 normal/7 increased, capillary electrophoresis: 48 normal CDT results. After combining an immunological CDT test (microcolumn+TIA or particle-enhanced immunonephelometry) as the screening method with a physico-chemical CDT test (HPLC or electrophoresis) as the confirmatory method, 1 case remained with increased CDT values by the screening (value 2.6%, cut-off 2.5%, particle-enhanced immunonephelometry) and confirmatory (value 1.8%, cut-off 1.75%, HPLC) analysis.

CONCLUSIONS

PBC should no longer be overstressed as an important cause for false-positive CDT results regarding chronic alcohol abuse. In the presence of odd CDT results, PBC should be considered in the anamnestic exploration. However, PBC is not by itself a cause for increased CDT values.

Progress in capillary electrophoresis of biomarkers and metabolites between 2002 and 2005

Biomarker discovery and metabolite research is a fast-growing and extremely important domain not only for the early detection of certain diseases but also for controlling its progress as well as in pharmaceutical investigations. For the analytical separation and identification, CE plays an indisputable role. Capillary systems enhancing different selectivity are applied and connected to different kind of detection systems. As the choice of buffer and its composition is responsible for a successful separation, special emphasis is put on solvent effects in this review. Altogether the most important capillary electrophoretic techniques applied for biomarker and metabolites analysis published between 2002 and 2005 are summarized and discussed.

The significance of serum gamma-glutamyltransferase in cardiovascular diseases

Since early after the introduction of serum gamma-glutamyltransferase (GGT) in clinical practice as a reliable and widely employed laboratory test, epidemiological and prospective studies have repeatedly shown that this activity possesses a prognostic value for morbidity and mortality. The association is independent of possibly concomitant conditions of liver disease, and notably, a significant independent correlation of serum GGT exists with the occurrence of cardiovascular diseases (myocardial infarction, stroke). Experimental work has documented that active GGT is present in atherosclerotic plaques of coronary as well as in cerebral arteries. These findings, and the recently recognized functions of GGT in the generation of reactive oxygen species, indicate that serum GGT represents a true marker of cardiovascular diseases and underlying atherosclerosis. Further insights into potential therapeutic interest will probably be derived from studies investigating the origin of GGT activity in plaque tissue.