Capillary electrophoresis-based separation of transferrin sialoforms in patients with carbohydrate-deficient glycoprotein syndrome

Biochemical diagnosis of congenital disorders of glycosylation

Congenital disorders of glycosylation (CDG) are one of the fastest growing groups of inborn errors of metabolism, comprising over 160 described diseases to this day. CDG are characterized by a dysfunctional glycosylation process, with molecular defects localized in the cytosol, the endoplasmic reticulum, or the Golgi apparatus. Depending on the CDG, N-glycosylation, O-glycosylation and/or glycosaminoglycan synthesis can be affected. Various proteins, lipids, and glycosylphosphatidylinositol anchors bear glycan chains, with potential impacts on their folding, targeting, secretion, stability, and thus, functionality. Therefore, glycosylation defects can have diverse and serious clinical consequences. CDG patients often present with a non-specific, multisystemic syndrome including neurological involvement, growth delay, hepatopathy and coagulopathy. As CDG are rare diseases, and typically lack distinctive clinical signs, biochemical and genetic testing bear particularly important and complementary diagnostic roles. Here, after a brief introduction on glycosylation and CDG, we review historical and recent findings on CDG biomarkers and associated analytical techniques, with a particular emphasis on those with relevant use in the specialized clinical chemistry laboratory. We provide the reader with insights and methods which may help them properly assist the clinician in navigating the maze of glycosylation disorders.

Chitosan derivatives as dynamic coatings for transferrin glycoform separation in capillary electrophoresis

Chitosan and its derivatives are interesting biopolymers for different field of analytical chemistry, especially in separation techniques. The present study was aimed at testing chitosan water soluble derivatives as dynamic coating agents for application to capillary electrophoresis. In particular, chitosan was modified following three different chemical reactions (nucleophilic substitution, reductive amination, and condensation) to introduce differences in charge and steric hindrance, and to assess the effect of these physico-chemical properties in capillary electrophoresis. The effects were tested on the capillary electrophoretic separation of the glycoforms of human transferrin, an important iron-transporting serum protein, one of which, namely disialo-transferrin (CDT), is a biomarker of alcohol abuse. Chitosan derivatives were characterized by using NMR and 1H NMR, HP-SEC-TDA, DLS, and rheology. The use of these compounds as dynamic coatings in the electrolyte running buffer in capillary electrophoresis was tested assessing the peak resolution of the main glycoforms of human transferrin and particularly of disialo-transferrin. The results showed distinct changes of the peak resolution produced by the different derivatives. The best results in terms of peak resolution were achieved using polyethylene glycol (PEG)-modified chitosan, which, in comparison to a reference analytical approach, provided an almost baseline resolution of disialo-transferrin from the adjacent peaks.

High-resolution capillary zone electrophoresis and mass spectrometry for distinction of undersialylated and hypoglycosylated transferrin glycoforms in body fluids

High-resolution capillary zone electrophoresis is used to distinguish transferrin glycoforms present in human serum, cerebrospinal fluid, and serum treated with neuraminidase and N-glycosidase F. The obtained data are compared to mass spectrometry data from the literature. The main focus is on the analysis of the various asialo-transferrin, monosialo-transferrin, and disialo-transferrin molecules found in these samples. The features of capillary zone electrophoresis and mass spectrometry are reviewed and highlighted in the context of the analysis of undersialylated and hypoglycosylated transferrin molecules. High-resolution capillary zone electrophoresis represents an effective tool to assess the diversity of transferrin patterns whereas mass spectrometry is the method of choice to elucidate structural identification about the glycoforms. Hypoglycosylated transferrin glycoforms present in sera of alcohol abusers and normal subjects are structurally identical to those in sera of patients with a congenital disorder of glycosylation type I. Asialo-transferrin, monosialo-transferrin and disialo-transferrin observed in sera of patients with a type II congenital disorder of glycosylation or a hemolytic uremic syndrome, in cerebrospinal fluid and after treatment of serum with neuraminidase are undersialylated transferrin glycoforms with two N-glycans of varying structure. Undersialylated disialo-transferrin is also observed in sera with high levels of trisialo-transferrin.

Fast screening of N-glycosylation disorders by sialotransferrin profiling with capillary zone electrophoresis

Background Congenital disorders of glycosylation (CDG) are a growing group of rare genetic disorders. The most frequently used screening method is sialotransferrin profiling using isoelectric focusing (IEF). Capillary zone electrophoresis (CZE) may be a simple and fast alternative. We investigated the Capillarys™ CDT assay (Sebia, France) to screen for N-glycosylation disorders, using IEF as gold standard. Methods Intra- and inter-assay precision were established, and analyses in heparin-anticoagulated plasma and serum were compared. Accuracy was assessed by comparing IEF and CZE profiles of 153 samples, including 49 normal, 53 CDG type I, 2 CDG type II, 1 combined CDG type I and type II and 48 samples with a Tf-polymorphism. Neuraminidase-treated plasma was analysed to discriminate CDG and Tf-polymorphisms using samples of 52 subjects (25 had a confirmed Tf-polymorphism). Age-dependent reference values were established using profiles of 312 samples. Results Heparin-plasma is as suitable as serum for CDG screening with the Capillarys™ CDT assay. The precision of the method is high, with a limit of quantification (LOQ) of 0.5%. All profiles, including CDG and Tf-polymorphisms, were correctly identified with CZE. Forty-nine of 52 neuraminidase-treated samples correctly identified the presence/absence of a Tf-polymorphism. Interferences in 3/52 samples hampered interpretation. Sialo-Tf profiles were dependent of age, in particular in the first three months of age. Conclusions CZE analysis with the Capillarys™ CDT kit (Sebia) is a fast and reliable method for screening of N-glycosylation defects. Tf-polymorphisms could be excluded after overnight incubation with neuraminidase.

High-resolution capillary zone electrophoresis for transferrin glycoform analysis associated with congenital disorders of glycosylation

High-resolution capillary zone electrophoresis is used to assess the transferrin profile in serum of patients with eight different congenital disorders of glycosylation that represent type I, type II, and mixed type I/II disorders. Capillary zone electrophoresis data are compared to patterns obtained by gel isoelectric focusing. The high-resolution capillary zone electrophoresis method is shown to represent an effective tool to assess the diversity of transferrin patterns. Hypoglycosylated disialo-, monosialo-, and asialo-transferrin in type I cases can be distinguished from the corresponding underdesialylated transferrin glycoforms present in type II disorders. The latter can be separated from and detected ahead of their corresponding hypoglycosylated forms of type I patients. Both types of glycoforms are detected in sera of mixed type I/II patients. The assay has the potential to be used as screening method for congenital disorders of glycosylation. It can be run with a few microliters of serum when microvials are used.

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.

Transferrin-immune complex disease: a potentially overlooked gammopathy mediated by IgM and IgG

The combination of marked hypersideremia, hypertransferrinemia, and monoclonal gammopathy of underdetermined significance (MGUS) should alert clinicians to the possible presence of an anti-transferrin immunoglobulin, an uncommon acquired disorder also defined as transferrin-immune complex disease (TICD). The authors have previously described a case of TICD with 100% transferrin saturation and liver iron overload. However, the findings in the few cases so far reported are heterogeneous, and the presence of high transferrin saturation and liver iron overload is not universal. In this article, the authors have described the identification of two additional patients with anti-transferrin monoclonal gammopathy, hypersideremia, and hypertransferrinemia, but with incomplete transferrin saturation and no hepatic iron overload. The autoantibodies were purified by using transferrin as affinity bait and characterized. One subject showed a high-titer monoclonal anti-transferrin IgM with a κ-type light chain. This finding is the first observation of IgM autoantibodies against transferrin. The other patient developed the disease after pregnancy. In this study, monoclonal antibody was an IgG mounting a κ-type light chain with altered molecular weight. These results highlight that transferrin might induce the development of a monoclonal immune response of different classes and specificity. The identification, in a single hematologic center, of three different subjects with anti-transferrin monoclonal gammopathy suggests that the disease probably represents a still underdiagnosed condition. From a clinical standpoint, these patients must be followed up both as MGUS and as hemochromatosis.

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.

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.

Development and multicenter evaluation of the N latex CDT direct immunonephelometric assay for serum carbohydrate-deficient transferrin

BACKGROUND

Carbohydrate-deficient transferrin (CDT) is a promising biomarker of alcohol abuse. We describe the development and multicenter evaluation of N Latex CDT (Dade Behring), an automated, particle-enhanced, homogeneous immunonephelometric assay for directly determining CDT.

METHODS

N Latex CDT uses a monoclonal antibody that recognizes the structure of transferrin glycoforms lacking 1 or 2 complete N-glycans [i.e., disialo-, monosialo-, and asialotransferrins (CDT glycoforms)] in combination with a simultaneous assay for total transferrin. The Dade Behring BN II and BN ProSpec systems automatically calculate the CDT value as a percentage of total transferrin (%CDT). No preanalytical sample treatment is used.

RESULTS

Total imprecision values for serum pools containing 1.8%-8.7% CDT were 3.4%-10.4% (mean, 6.8%). The mean (SD) %CDT for 561 serum samples from healthy control individuals was 1.76% (0.27%; range, 1.01%-2.85%). No marked sex or age differences were noted. The 97.5th percentile was at 2.35%. Transferrin genetic variants did not interfere with measurements. High transferrin concentrations did not falsely increase %CDT values, but increased %CDT values were noted for some samples with transferrin concentrations <1.1 g/L. N Latex CDT results correlated with those of a commercial CDT immunoassay involving column separation (r(2) = 0.862) and an HPLC candidate reference method (r(2) = 0.978).

CONCLUSION

N Latex CDT is the first direct immunoassay for quantifying %CDT in serum. The specificity of N Latex CDT for identifying alcohol abuse may be higher than for immunoassays that use column separation, because transferrin genetic variants do not interfere with measurements.

Capillary zone electrophoresis determination of carbohydrate-deficient transferrin using the new CEofix reagents under high-resolution conditions

Capillary zone electrophoresis (CZE) with a dynamic double coating based on the new CEofix reagents is shown to provide high-resolution separations of serum transferrin (Tf) isoforms, a prerequisite for the monitoring of unusual and complex Tf patterns, including those seen with genetic variants and disorders of glycosylation. A 50 microm I.D. fused-silica capillary of 60 cm total length, an applied voltage of 20 kV and a capillary temperature of 30 degrees C results in 15 min CZE runs of high assay precision and thus provides a robust approach for the determination of carbohydrate-deficient transferrin (CDT, sum of asialo-Tf and disialo-Tf in relation to total Tf) in human serum. Except for selected samples of patients with severe liver diseases and sera with high levels of paraproteins, interference-free Tf patterns are detected. Compared with the use of the previous CEofix reagents for CDT under the same instrumental conditions, the resolution between disialo-Tf and trisialo-Tf is significantly higher (1.7 versus 1.4). The CDT levels of reference and patient sera are comparable, suggesting that the new assay can be applied for screening and confirmation analyses. The high-resolution CZE assay represents an attractive alternative to HPLC and can be regarded as a candidate of a reference method for CDT.

Detection of transferrin isoforms in human serum: comparison of UV and ICP–MS detection after CZE and HPLC separations

Two methods for separation of transferrin (Tf) sialoforms, capillary electrophoresis (CE) and high performance liquid chromatography (HPLC) with conventional UV absorbance detection, have been investigated and compared. First, conditions affecting the separation of the Tf isoforms by capillary zone electrophoresis and HPLC were carefully optimized. The use of 15 mmol L(-1) borate buffer (pH 8.4) containing 3 mmol L(-1) diaminobutane (DAB) as additive enabled good separation of the Tf isoforms by CE (75 cm x 50 microm i.d. fused silica capillary) at 25 kV. In HPLC, a gradient of ammonium acetate (from 0 to 250 mmol L(-1) in 45 min) buffered at pH 6 (Tris-HCl) proved suitable for separation of Tf isoforms on a Mono-Q HR 5/5 anion-exchange column. On-line specific detection of the iron associated with the different Tf isoforms, after Fe saturation, by inductively coupled plasma mass spectrometry (ICP-MS) was studied in detail to compare its analytical performance with UV detection. For both CE and HPLC an octapole reaction system (ORS) ICP-MS instrument was used to minimize polyatomic interferences on the (56)Fe major isotope. Limits of detection of the different isoforms were in the range of 0.02-0.04 micromol L(-1) Tf for HPLC-ICP (ORS)-MS. This hybrid technique proved more selective and reliable detection of transferrin isoforms with 2, 3, 4, 5, and 6 sialic acid residues (S(2), S(3), S(4), S(5), and S(6)) in real serum samples. Interesting results from iron speciation of Tf in serum from healthy individuals and from pregnant women are given.

Carbohydrate-deficient transferrin (CDT)--a biomarker for long-term alcohol consumption

Carbohydrate-deficient transferrin (CDT) is a biomarker for chronic alcohol intake of more than 60 g ethanol/d. It has been reported to be superior to conventional markers like gamma-glutamyltransferase (GGT) and mean corpuscular volume MCV). This review covers theoretical and analytical aspects, with data from controlled drinking experiments and from different population subgroups such as subjects with different liver diseases or different drinking patterns. CDT determinations are particularly indicated in (1) cases of chronic alcohol consumption and relapses after withdrawal, (2) license reapplication after driving under alcohol influence, (3) differentiating patients with enzyme-inducing medication from those with alcohol abuse, 4) congenital disorders of glycosylation such as carbohydrate-deficient glycoprotein syndrome Ia (CDGS Ia), and (5) patients treated for galactosemia. The main advantage of CDT is its high specificity, as evidenced in combination with increased alcohol consumption. CDT values are not markedly influenced by medication except in immunosuppressed patients, who may show low CDT values. In general, CDT values appear less elevated after alcohol intake in women. The main disadvantage is the relatively low sensitivity. Hence, this parameter is not suitable for screening for subjects with alcohol abuse in the general population. As CDT, GGT, and MCV are connected with chronic alcohol consumption by different pathophysiological mechanisms, a combination of these parameters will further improve the diagnostic value.

Diagnosis of Congenital Disorders of Glycosylation by Capillary Zone Electrophoresis of Serum Transferrin

Background: Congenital disorders of glycosylation (CDG) are usually diagnosed by isoelectric focusing (IEF) of serum transferrin (Tf). The aim of this study was to evaluate capillary zone electrophoresis (CZE) as a diagnostic alternative to IEF.

Methods: We performed 792 CZE analyses of Tf, using the CEofixTM-CDT (carbohydrate-deficient transferrin) assay. Peak identification was based on relative migration times (RMTs) to reduce migration variability.

Results: Tf profiles comprised three main groups (A–C). Groups A and B were characterized by one or two dominant tetrasialo-Tf peaks, whereas group C showed a widely variable Tf isoform composition. Group A was composed of four subgroups: a major group with a typical Tf profile (considered as reference group), two minor groups with decreased or moderately increased trisialo-Tf isoform, and a group showing the presence of unknown compounds with RMTs similar to mono- and disialo-Tf. However, these compounds were absent on IEF. Group C contained all profiles from patients with confirmed as well as putative CDG. From the reference group, 99% confidence intervals were calculated for the RMTs of the Tf isoforms, and percentiles representing the Tf isoform distributions were defined.

Conclusions: All patients with abnormal IEF results and confirmed CDG were identified by CZE; thus, this method can be used as a diagnostic alternative to IEF in a manner suitable for automation. Because whole serum is analyzed, it should be kept in mind that CZE profiles can show substances other than Tf.

Capillary zone electrophoresis with a dynamic double coating for analysis of carbohydrate-deficient transferrin in human serum

Capillary zone electrophoresis (CZE) with a dynamic double coating permits the simultaneous, individual, quantitative determination of transferrin (Tf) isoforms in human serum and thus carbohydrate-deficient transferrin (CDT), the most specific marker available today for the detection of chronic, excessive alcohol intake. CZE of serum Tf was carefully evaluated using the P/ACE MDQ with fused-silica capillaries of 50 microm I.D. and 60.2 cm total length, the CEofix CDT kit and the instrumental conditions recommended by the kit manufacturer. The precision performance assessed over a 20-day period according to the internationally accepted NCCLS EP5-A guidelines revealed the CZE assay as being highly reproducible with within-run and total precision being dependent on the Tf isoform level and RSD values ranging between 2.2 and 17.6%. Inter-day RSD values for asialo-Tf were noted to be between 9.8 and 11.5% and for disialo-Tf between 3.8 and 8.6%, whereas those for CDT levels of 0.87 and 4.31% of total Tf were determined to be 8.6 and 3.4%, respectively. The RSD values for trisialo-Tf, tetrasialo-Tf, pentasialo-Tf and hexasialo-Tf were found to be between 0.4 and 4.1%. Tf patterns are recognized and identified via detection times of Tf isoforms (intra-day and inter-day RSD values < 1.0% and < 1.7%, respectively), immunosubtraction of Tf and enzymatic sequential cleavage of sialic acid residues. Furthermore, heterozygous Tf BC and Tf CD variants are assigned via spiking with a known mixture of Tf isoforms (e.g. the serum of a healthy Tf C homozygote). Among the non-Tf peaks monitored, the CRP peak detected shortly before disialo-Tf was identified by immunosubtraction and peak magnitudes were found to correlate well with immunochemically determined CRP serum levels. The CZE assay with dynamic double coating could thereby be shown to be sensitive enough to determine elevated CRP levels in human serum. Furthermore, unusual peaks in the gamma-region were identified by customary serum protein CZE, immunosubtraction CZE and immunofixation.

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.

Capillary electrophoresis and its application in the clinical laboratory

Over the past 10 years, capillary electrophoresis (CE) is an analytical tool that has shown great promise in replacing many conventional clinical laboratory methods, especially electrophoresis and high performance liquid chromatography (HPLC). The main attraction of CE was that it was fast, used small amounts of sample and reagents, and was extremely versatile, being able to separate large and small analytes, both neutral and charged. Because of this versatility, numerous methods for clinically relevant analytes have been developed. However, with the exception of the molecular diagnostic and forensic laboratories CE has not had a major impact. A possible reason is that CE is still perceived as requiring above-average technical expertise, precluding its use in a laboratory workforce that is less technically adept. With the introduction of multicapillary instruments that are more automated, less technique-dependent, in addition to the availability of commercial and cost effective test kit methods, CE may yet be accepted as a instrument routinely used in the clinical laboratories. Thus, this review will focus on the areas where CE shows the most potential to have the greatest impact on the clinical laboratory. These include analysis of proteins found in serum, urine, CSF and body fluids, immunosubstraction electrophoresis, hemoglobin variants, lipoproteins, carbohydrate-deficient transferrin (CDT), forensic and therapeutic drug screening, and molecular diagnostics.

Biochemical markers of alcohol use in pregnant women

OBJECTIVES

To describe the serious health consequences of alcohol (ethanol) use, especially as they relate to pregnancy and the development of fetal alcohol syndrome (FAS) and fetal alcohol effects (FAE). The classic markers of alcohol exposure, including blood/breath alcohol, gamma-glutamyl transferase (gammaGT), mean corpuscular volume (MCV), hemoglobin-associated acetaldehyde (HAA) and carbohydrate deficient transferrin (CDT), are valuable and their methods of analysis are reviewed.

CONCLUSIONS

Since both FAS and FAE represent two of the leading preventable causes of mental retardation and birth defects, identification of alcohol use early in pregnancy is important to avoid adverse fetal outcomes. Unfortunately, the diagnosis of FAS and FAE is usually made after birth, when alcohol damage has become irreversible and permanent. The clinical laboratory can help prevent this damage and make a valuable contribution in assessing prenatal alcohol use. The clinical utility of blood/breath alcohol, gammaGT, MCV, HAA and CDT in alcohol use identification, especially in pregnancy, is substantial. Although none of the markers singularly has adequate sensitivity and specificity for screening, their diagnostic utility increases when measured as a panel. This is especially true in detecting alcohol use in pregnancy where the presence of several positive markers was correlated with the presence of alcohol-related fetal effects.

Evaluation and optimization of capillary zone electrophoresis with different dynamic capillary coatings for the determination of carbohydrate-deficient transferrin in human serum

Serum transferrin (Tf) comprises several isoforms with up to two complex oligosaccharide chains containing zero to eight sialic acid residues and neutral sugars. The major glycoform, known as tetrasialo-Tf, contains four sialic acid residues and accounts for about 80% of whole Tf in human serum. Carbohydrate-deficient transferrin (CDT) encompasses isoforms that are deficient in carbohydrate chains and consequently in sialic acid residues (including asialo-, monosialo- and disialo-Tf) and is a well known marker for chronic alcohol abuse. Recently capillary zone electrophoresis (CZE) has been reported as a tool extremely effective for the simultaneous, individual, quantitative determination of CDT isoforms. Three CZE methods that feature different dynamic capillary coatings were evaluated and optimized for CDT determination in human serum of alcohol abusers and control subjects. CZE separation was performed in alkaline borate buffers after serum sample saturation with iron, electropherograms were detected at 200 nm, data were evaluated as % area of disialo-Tf in relation to tetrasialo-Tf and peak identification was accomplished via relative migration times to tetrasialo-Tf, immunosubtraction and enzymatic sequential cleavage of sialic acid residues. Dynamic capillary coatings with diaminobutane, spermine and a double coating produced by commercially available proprietary agents were investigated and found to be suitable for determination of CDT in human serum. For all three approaches, best results were obtained in 50 microm I.D. fused-silica capillaries of 50 cm effective length and a capillary cartridge temperature of 20-25 degrees C. Using 3 mM 1,4-diaminobutane or 0.02 mM spermine in a borate-based running buffer of pH 8.3 provided data of remarkable similarity with resolution of di-, tri-, tetra- and pentasialo-Tf within 15-18 min. With the double coating, asialo-Tf and Tf isoforms with two to six sialic acid residues were baseline separated. Compared to the two amine-based procedures, the run times were found to be somewhat shorter, the detector signals higher, the applied power level significantly lower and the reproducibility better.

Chromatographic methods for the determination of markers of chronic and acute alcohol consumption

The development in chromatographic methods for the determination of markers of alcohol consumption is summarized in this review. The markers included in this article are ethanol in body fluids, ethanol congeners, fatty acid ethyl esters (FAEEs), ethyl glucuronide (EtG), cocaethylene (CE), carbohydrate-deficient transferrin (CDT), phosphatidylethanol (PEth), 5-hydroxytryptophol (5-HTOL), dolichol, ketone bodies, acetaldehyde-protein adducts, and salsolinol (SAL). Some of these markers for alcohol consumption do not only indicate previous ethanol ingestion, but also approximate the amount of intake and the time when ethanol ingestion last occurred. Basic information about the procedures, work-up, and chromatographic conditions are summarized in tables. Also the main metabolic pathways and reaction schemes are demonstrated in figures. Some examples of typical applications are presented. The author points out that in many of the reviewed papers validation data of the procedures as well as specificities and sensitivities were not clearly presented and consequently were not comparable.

Carbohydrate-deficient Transferrin Isoforms Measured by Capillary Zone Electrophoresis for Detection of Alcohol Abuse

Background: Measurements of carbohydrate-deficient transferrin (CDT) are used as markers of alcohol abuse. We developed a capillary zone electrophoresis (CZE) method aimed at improving accuracy of CDT testing.

Methods: We studied 111 alcohol abusers with Alcohol Use Disorders Identification Test scores &gt;11 and 50 teetotalers. CZE was performed with a P/ACE 5500, fused-silica capillaries, and a CEofix CDT reagent set. After iron saturation, sera were loaded by low-pressure injection, separated at 28 kV, and monitored at 214 nm. We identified the transferrin isoforms by migration times, treatment with 100 U/L neuraminidase, and immunosubtraction with anti-human transferrin and anti-C-reactive protein antibodies. We compared CZE results with current biological markers of alcohol abuse, including the %CDT turbidimetric immunoassay.

Results: Migration times of the isoforms were identical in both populations. Asialotransferrin was missing in teetotalers but present in 92% of alcohol abusers. Disialotransferrin was higher in those who consumed excessive amounts of alcohol, whereas mean trisialotransferrin concentration was not affected by alcohol abuse. At cutoffs to maximize sensitivity and specificity, these values were 0.92 and 1 [mean ROC area (MRa), 0.96; 95% confidence interval (CI), 0.93–0.99] for asialotransferrin; 0.84 and 0.94 for the sum of asialo- + disialotransferrin (MRa, 0.94; 95% CI, 0.91–0.98); 0.79 and 0.94 for disialotransferrin (MRa, 0.89; 95% CI, 0.84–0.94); 0.62 and 0.53 for trisialotransferrin (MRa, 0.58; 95% CI, 0.49–0.68); 0.79 and 0.82 for a 3% %CDT; and 0.83 and 0.69 for a 2.6% cutoff (MRa, 0.87; 95% CI, 0.81–0.92). Current markers lack sensitivity (&lt;0.65). Transferrins were not significantly correlated with serum enzymes and mean erythrocyte volume.

Conclusions: CZE-isolated desialylated transferrin isoforms allowed differentiation between chronic alcohol abusers and teetotalers.

Congenital disorders of glycosylation: a review

Congenital disorders of glycosylation (CDGs) are a rapidly growing group of inherited disorders caused by defects in the synthesis and processing of the asparagine(ASN)-linked oligosaccharides of glycoproteins. The first CDG patients were described in 1980. Fifteen years later, a phosphomannomutase deficiency was found as the basis of the most frequent type, CDG-Ia. In recent years several novel types have been identified. The N-glycosylation pathway is highly conserved from yeast to human, and the rapid progress in this field can largely be attributed to the systematic application of the knowledge of yeast mutants. Up to now, eight diseases have been characterized, resulting from enzyme or transport defects in the cytosol, endoplasmic reticulum, or Golgi compartment. CDGs affect all organs and particularly the CNS, except for CDG-Ib, which is mainly a hepatic-intestinal disease.

Determination of CDT, a marker of chronic alcohol abuse, for driving license issuing: immunoassay versus capillary electrophoresis

The present work is aimed at a validation of the carbohydrate-deficient transferrin (CDT) determination in real cases by comparison between the a commercial immunometric method and a method based on capillary electrophoresis. Overall, 650 serum samples from subjects applying to re-obtain their driving license, previously withdrawn for "drunk driving", were investigated. A highly significant correlation (P < 0.001) was found between the results from immunoassay and capillary electrophoresis. However, particularly in the samples with CDT values around the cut-off or moderately elevated, a wide dispersion of the correlation data was found. This finding stresses the need to confirm by alternative techniques all the results from CDT immunoassays. For this purpose, capillary electrophoresis, because of its inherent characteristics of high selectivity, easy operation, high productivity and low operative costs looks well-suited for becoming the method of choice.

Online single-step analysis of blood proteins: the transferrin story

The serum iron transport protein human transferrin (hTf) is a glycoprotein (MW approximately 79.6 kDa) containing two Asn-linked sites of glycosylation. The presence of specific glycoforms of hTf has been used as an indicator of carbohydrate-deficient glycoprotein syndrome (CDGS) or an indicator of alcohol abuse. The exact nature of the glycoforms described in the literature is controversial. In this work we demonstrate that the altered hTf glycoforms have lost one or both complete glycan side chains. Furthermore, we demonstrate using a combination of online immunoaffinity-postconcentration-mass spectrometry in conjunction with a blood spot cartridge that we can determine the relative quantities of the hTf glycoforms using <5 microL blood in under 30 min. This is in contrast to previous methods that used 1 mL and took 4 days. We show that this method can be useful to analyze hTf from CDGS and alcoholic patients.

Routine differential diagnosis of proteinurias by capillary electrophoresis

Capillary electrophoresis is a relatively new analytical technique that begins to have an impact on both routine and research in clinical laboratories. Recently, a fully automated system has become commercially available (Paragon CZE 2000, Beckman, USA) for the analysis of human serum proteins. Urine protein analysis, on the other hand, is currently accomplished by electrophoresis of concentrated urine specimens. The method is used to distinguish the glomerular from the tubular proteinuria and for the identification of Bence-Jones proteins. The procedure is labor-intensive and technically demanding. We developed a technique for the serum capillary electrophoresis instrument that can also be applied routinely to the differential diagnosis of proteinurias. Overriding the programmed dilution step of the instrument, we were able to distinguish different types of proteinurias without concentration of specimens with a total protein content of 150-200 mg/l as determined by sulfosalicylic acid. The different electrophoretic patterns obtained by the capillary electrophoresis system for various specimens correlated well with established techniques (Hydragel Proteinurie Kit, Sebia, France). The method is applicable for routine analysis of urinary proteins. It is reliable, less expensive and faster than the conventional methods (electrophoretic or immunonephelometric) used today for the differentiation of proteinurias, and it can be used as a quick screening test.

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.

Carbohydrate-deficient Transferrin as a Marker of Chronic Alcohol Abuse: A Critical Review of Preanalysis, Analysis, and Interpretation

Background: Carbohydrate-deficient transferrin (CDT) is used for diagnosis of chronic alcohol abuse. Some 200–300 reports on CDT have been published in impact factor-listed journals. The aims of this review were to condense the current knowledge and to resolve remaining issues on CDT.

Approach: The literature (1976–2000) was searched using MEDLINE and Knowledge Server with “alcohol and CDT” as the search items. The data were reviewed systematically, checked for redundancy, and organized in sequence based on the steps involved in CDT analysis.

Content: The review is divided into sections based on microheterogeneity of human serum transferrin (Tf), definition of CDT, structure of human serum CDT, pathomechanisms of ethanol-induced CDT increase, preanalysis, analysis, and medical interpretation (postanalysis). Test-specific cutoff values for serum CDT and causes of false positives and negatives for chronic alcohol abuse are discussed and summarized.

Summary: Asialo- and disialo-Fe2-Tf, which lack one or two complete N-glycans, and monosialo-Fe2-Tf (structure remains unclear) are collectively referred to as CDT. Diminished mRNA concentration and glycoprotein glycosyltransferase activities involved in Tf N-glycan synthesis and increased sialidase activity most likely account for alcohol-induced increases in CDT. Knowledge about in vivo and in vitro effects on serum CDT is poor. Reliable CDT and non-CDT fractionation is needed for CDT measurement. Analysis methods with different analytical specificities and recoveries decreased the comparability of values and statistical parameters of the diagnostic efficiency of CDT. CDT is the most specific marker of chronic alcohol abuse to date. Efforts should concentrate on the pathomechanisms (in vivo), preanalysis, and standardization of CDT analysis.

Circumventing complement C3 interference in the analysis of carbohydrate-deficient transferrin in fresh serum

A method for preventing interference by the glycoprotein complement C3 and its beta-globulin split products in the capillary electrophoretic analysis of carbohydrate-deficient transferrin was developed. Inulin was used to activate the alternate complement pathway and convert native C3 into various degradation products whose electrophoretic mobility no longer coincides with the transferrin glycoforms. Capillary electrophoresis and zone electrophoresis on agarose gel were used to monitor reaction conditions for alternate complement pathway activation. Incubation of 50 microL of fresh serum with 180 microL of a 50 mg/mL inulin slurry for 12 h removed the native C3 peak from the beta region. Inulin treatment did not affect electrophoretic behavior of other beta-globulins, including transferrin. Altering the electrophoretic behavior of complement C3, by treating fresh serum with inulin, permits rapid capillary electrophoresis evaluation of carbohydrate-deficient transferrin glycoforms.

Direct capillary electrophoretic detection of carbohydrate-deficient transferrin in neat serum

Transferrin, an iron transport protein found in serum and cerebrospinal fluid, is known to be microheterogeneous with respect to its carbohydrate and sialic acid content. The forms of transferrin deficient in sialic acid and/or carbohydrate, termed carbohydrate-deficient transferrin (CDT), have been of clinical interest for almost two decades as a result of the initial finding that elevated CDT concentrations are associated with chronic, excessive alcohol abuse. We demonstrate the utility of capillary electrophoresis for examining the CDT sialoform profile via the direct electrophoresis of serum. The need for negligible preelectrophoresis sample preparation and absence of postelectrophoresis processing dramatically decreases analysis time compared to slab gel-based separations. Using a fluorocarbon-coated capillary containing a hydroxyethyl cellulose/borate buffer, the high resolution separation of serum components is effected in less than 30 min. Under these conditions, the beta region proteins (including transferrin) are well resolved from the alpha-2 and gamma zone proteins in a window where the individual transferrin sialoforms can be detected. The usefulness of this method is demonstrated with the electrophoresis of serum from subjects known to be either non-alcoholic and alcoholic.

Dynamically-coated capillaries allow for capillary electrophoretic resolution of transferrin sialoforms via direct analysis of human serum

Transferrin sialoforms with fewer than three sialic acid residues (carbohydrate deficient transferrin; CDT) have been implicated as a marker of certain liver pathologies. Transferrin sialoforms in human sera from alcoholic and non-alcoholic patients was analyzed by capillary electrophoresis (CE) using diaminobutane (DAB) to dynamically-coat the capillary wall to minimize protein-wall interactions. Using a DAB concentration of 3 mM, transferrin sialoforms were adequately resolved to allow for direct detection of CDT without extensive treatment of the sera. Serum immunoglobulins, which migrated close to the CDT region, were removed via subtraction with protein A, enhancing the detection of CDT. The reproducibility of sialoform separation in dynamically-coated capillaries was found to be acceptable with run-to-run relative standard deviation values of 0.15% for a sample on a given day and 0.29+/-0.06% for four samples day-to-day. These results suggest that dynamic-coating approaches may provide a simple alternative to the use of covalently-coated capillaries for the CE separation of complex samples.

Improved method for carbohydrate-deficient transferrin determination in human serum by capillary zone electrophoresis

Carbohydrate-deficient transferrin (CDT) is a reliable marker of chronic or repeated alcohol abuse. It indicates a group of isoforms of human transferrin (Tf), the main iron transport serum protein, deficient in sialic acid residues (asialo-, monosialo- and disialo-Tf) in comparison to the main isotransferrin which contains four sialic acid groups (tetrasialo-Tf). The aim of the present work was to develop a capillary electrophoretic method suitable for rapid determination of CDT components in serum. Serum samples (0.1 ml) were saturated with iron by incubation with 10 mM FeCl3 (2 microl) and 500 mM NaHCO3 (3 microl) for 30 min, then diluted 1:10 in water and injected by positive pressure (0.5 p.s.i. for 10 s). Separation was performed with a capillary zone electrophoretic method using bare fused-silica capillaries (57 cm x 20 microm I.D.) and a buffer composed of 100 mM sodium tetraborate adjusted with 6 M HCl to pH 8.3 added with 1.5 mM diaminobutane. Applied voltage was 20 kV and temperature 25 degrees C. Detection was by UV absorption at 200 nm wavelength. Under the described conditions, asialo-, monosialo-, disialo-, trisialo- and tetrasialo-transferrin were baseline separated. The limit of detection (signal-to-noise ratio of 2) was about 0.3% for disialo-Tf, and 0.5% of trisialo-Tf, expressed as percentages of the terasialo-Tf peak area. Day-to-day RSDs of relative migration times were < or = 0.2%. Quantitation showed day-to-day RDSs < or = 6.9% and < or = 10.9% for disialo- and trisialo-Tf, respectively. The results from 79 control subjects, including social drinkers, and 23 alcoholics showed disialo- and trisialo-Tf significantly increased in patients (P<0.0001 and <0.01, respectively). A clear interference from trisialo-Tf in an immunoassay for CDT was demonstrated. The present method is suitable for confirmation of CDT immunoassays by independent technique.

Strategies for analysis and structure characterization of glycans/proteoglycans by capillary electrophoresis. Their diagnostic and biopharmaceutical importance

Proteoglycans are key biological macromolecules that, via their glycan constituents, participate and regulate several cellular events and physiopathological processes. Refined structures of their highly anionic glycan chains, involving sulphation pattern and uronic acid distribution through the polymeric chain, determine the interactions of proteoglycans with matrix effector molecules and are responsible for numerous effects. Analysis and structural characterization of glycans are, therefore, essential in understanding the biological functions of proteoglycans. Capillary electrophoresis with its high resolving power and sensitivity may successfully be used for the fine chemical characterization of components present in low amounts and to overcome limitations due to low amount/volume of biologic samples available. This technique is also friendly to the user and to the environment, since a very small amount of solvents (a few microL) is required. In this review the strategies used to analyse and characterize the structure of glycan chains of proteoglycans are summarized. They involve capillary electrophoretic analysis of depolymerized acidic glycan chains using specific enzymes and analysis of intact chains. The importance of this type of analysis in biologic samples and tissues and its possible diagnostic and biopharmaceutical use are also discussed.

Carbohydrate-deficient glycoprotein syndrome type II

The carbohydrate-deficient glycoprotein syndromes (CDGS) are a group of autosomal recessive multisystemic diseases characterized by defective glycosylation of N-glycans. This review describes recent findings on two patients with CDGS type II. In contrast to CDGS type I, the type II patients show a more severe psychomotor retardation, no peripheral neuropathy and a normal cerebellum. The CDGS type II serum transferrin isoelectric focusing pattern shows a large amount (95%) of disialotransferrin in which each of the two glycosylation sites is occupied by a truncated monosialo-monoantennary N-glycan. Fine structure analysis of this glycan suggested a defect in the Golgi enzyme UDP-GlcNAc:alpha-6-D-mannoside beta-1,2-N-acetylglucosaminyltransferase II (GnT II; EC 2.4.1.143) which catalyzes an essential step in the biosynthetic pathway leading from hybrid to complex N-glycans. GnT II activity is reduced by over 98% in fibroblast and mononuclear cell extracts from the CDGS type II patients. Direct sequencing of the GnT II coding region from the two patients identified two point mutations in the catalytic domain of GnT II, S290F (TCC to TTC) and H262R (CAC to CGC). Either of these mutations inactivates the enzyme and probably also causes reduced expression. The CDG syndromes and other congenital defects in glycan synthesis as well as studies of null mutations in the mouse provide strong evidence that the glycan moieties of glycoproteins play essential roles in the normal development and physiology of mammals and probably of all multicellular organisms.

Recent developments in capillary electrophoresis and capillary electrochromatography of carbohydrate species

This review article is concerned with the recent developments in capillary electrophoresis (CE) and capillary electrochromatography (CEC) of carbohydrates. The literature shows that CE possesses impressive potential in the analysis of carbohydrates. On the other hand, CEC has just started to show promise in the analysis of carbohydrates. Advances in separation and detection approaches of derivatized and underivatized carbohydrates are discussed based on the available literature. In addition, important applications are illustrated.

Recent developments in capillary zone electrophoresis of proteins

This review article with 125 references describes recent developments in capillary zone electrophoresis of proteins. It encompasses approximately the last two years, from the previous review (V. Dolník, Electrophoresis 1997, 18, 2353-2361) through Spring 1999. Topics covered include modeling of the electrophoretic properties of proteins, sample preconcentration and derivatization, wall coatings, improving selectivity, special detection techniques, and applications.

Capillary electrophoresis in clinical and forensic analysis: recent advances and breakthrough to routine applications

This paper is a comprehensive review article on capillary electrophoresis (CE) in clinical and forensic analysis. It is based upon the literature of 1997 and 1998, presents CE examples in major fields of application, and provides an overview of the key achievements encountered, including those associated with the analysis of drugs, serum proteins, hemoglobin variants, and nucleic acids. For CE in clinical and forensic analysis, the past two years witnessed a breakthrough to routine applications. As most coauthors of this review are associated with diagnostic or forensic laboratories now using CE on a routine basis, this review also contains data from routine applications in drug, protein, and DNA analysis. With the first-hand experience of providing analytical service under stringent quality control conditions, aspects of quality assurance, assay specifications for clinical and forensic CE and the pros and cons of this maturing, cost-and pollution-controlled age technology are also discussed.

Capillary electrophoresis of proteins for proteomic studies

Analyses of proteins in complex mixtures such as cell lyzates are presently performed mainly by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. For structural analysis, each protein in a spot is digested with proteases and the fragment peptides are subjected to Edman sequencing and/or mass spectrometry. These works aim at the total analysis of proteins in a complex mixture and reconstruction of their cooperative functions. Genomic studies are now being combined with these proteomic studies. This review article focuses on the application of capillary electrophoresis aiming at the total analysis of complex protein systems or structural analysis of each separated protein. From this viewpoint, articles on capillary zone electrophoresis, capillary isoelectric focusing, and sieving SDS capillary electrophoresis are reviewed. Since these techniques of capillary electrophoresis have been thoroughly reviewed previously, papers published in 1997 and 1998 are mainly covered.

Optimized determination of carbohydrate-deficient transferrin isoforms in serum by capillary zone electrophoresis

Carbohydrate deficient transferrin (CDT) is one of the most reliable markers of chronic alcohol abuse. It consists of a group of minor isoforms of human transferrin (the main iron transport serum protein) deficient in sialic acid groups (asialo, monosialo and disialo) with a pI > 5.7, while the main isotransferrin (tetrasialo) has a pI of 5.4. The aim of the present work was to develop a capillary electrophoretic method to determine CDT in serum, suitable for routine use as a confirmatory technique of the current screening methods based on immunoassays. Serum samples (0.5 mL) were saturated with iron by incubation with 10 mM FeCl3 (9 microL) and 500 mM NaHCO3 (12 microL) for 30 min, then diluted 1/10 in water and injected by positive pressure (0.5 psi for 10 s). Separation was performed with a capillary zone electrophoretic method using bare fused-silica capillaries (20 microm ID, 37 cm in length) and a buffer composed of 100 mM sodium tetraborate adjusted with boric acid to pH 8.3. Applied voltage was 10 kV and temperature 25 degrees C. Detection was by UV absorption at 200 nm wavelength. Under the described conditions, asialo-, monosialo-, disialo-, trisialo- and tetrasialo-transferrin were separated in human serum. The limit of detection (signal-to-noise ratio of 2) was about 0.3% for disialo-transferrin, and 0.4% of trisialo-transferrin, expressed as percentages of the terasialo-transferrin peak area. Relative standard deviations (RSD) of absolute migration times were < 1%, while RSD of relative migration times (on the basis of tetrasialo-transferrin) were < 0.1%. Intra-day and day-to-day peak quantitation precision studies showed RDS ranging from 4 to 9% and from 13 to 24% for disialo- and trisialo-transferrin, respectively. The results from 30 control subjects, including social drinkers, and 13 alcoholics showed disialo- and trisialo-transferrin significantly increased in patients by a factor of about 4.5 (P < 0.0001).

Capillary electrophoresis in drug analysis

Capillary electrophoresis has become one of the advanced analytical methods for drugs in pharmaceutical, therapeutic, diagnostic and forensic applications. This review discusses key issues and provides key references to the topic of drug analysis using capillary electrophoresis. It gives readers a brief summary of the current status of the technology and serves as an editorial for the paper symposium "Capillary electrophoresis in drug analysis".

Capillary electrophoresis as a clinical tool for the analysis of protein in serum and other body fluids

Most electrophoretic analyses of proteins in the clinical laboratory are currently carried out by electrophoresis in acrylamide or agarose gels. This labor-intensive method is now being challenged by capillary electrophoresis (CE) because of its potential for automated, rapid, high efficiency separations. The automatability of CE itself, combined with its amenability to interfacing with other robotized functions, positions this technology perfectly for the analysis of proteins in physiological matrices, such as serum, urine, and cerebrospinal fluid. The focus of this overview is to familiarize the clinical scientist with the research demonstrating the applicability of the technology to the clinical protein laboratory.

Analysis of carbohydrate deficient transferrin by capillary zone electrophoresis

We report a capillary zone electrophoresis method to separate the various sialylated isoforms of transferrin. The separation is carried out under nondenaturing conditions and at basic pH. Under these conditions, transferrin exhibits two major and three minor peaks. Plasma samples from a population consuming varying amounts of alcohol at different intervals were studied. A cut-off value of 3% carbohydrate deficient transferrin (CDT: disialo, monosialo, and asialo transferrin), results in a clinical sensitivity of 88% in a population consuming at least 70 g/day alcohol for a minimum of two weeks. The sensitivity dropped significantly in a population consuming less than 70 g/day. This confirms previous reports of CDT as a specific marker for significant and chronic use of alcohol. Capillary electrophoresis offers an alternative method with respect to analysis time and throughput in the clinical laboratory.