Capillary zone electrophoresis of serum proteins: effects of changed analytical conditions.

Analytical conditions in a system for capillary zone electrophoresis (Beckman Paragon CZE 2000) were originally selected to allow serum protein separation into five discrete protein zones, corresponding to those of conventional clinical electrophoresis. To improve the system's performance, new analytical conditions have been made available. We compared the two sets of conditions ("new" = y; "old" = x) for possible variations of results caused by the change. One hundred thirteen serum samples, covering wide intervals of values, were assayed on two twin instruments working under the old and the new conditions; results were assessed statistically and graphically. Possible clinical significance of differences was checked by comparison with the biological variation-based quality specifications for bias. Statistically significant (y-x) differences were observed for the alpha1-, alpha2- and beta-globulin zones; clinically significant differences were observed for all the zones, with the exception of the gamma-globulin zone. Therefore, old/new regression equations were calculated, whose reliability was assured by the wide interval of values, by the large sample size, and by the low dispersion of single values around the mean concordance estimates. Such equations may be used to convert "old" into "new" reference values, and for the intercomparison of patient results obtained under different analytical conditions.     

Detection of monoclonal proteins by capillary electrophoresis using a zwitterion in the running buffer

Some cases have been reported in which a small monoclonal protein (M-protein) cannot be detected by conventional cellulose acetate membrane electrophoresis (CAE) or capillary zone electrophoresis (CZE) using a short fused-silica capillary. This is probably because these methods do not have the necessary sensitivity or resolution. To overcome this problem, we improved the CZE system by using a longer capillary and adding a zwitterion to the running buffer (pH 10.0). A comparison of CZE and CAE demonstrated that with the exception of alpha(1)- and alpha(2)-globulin, the correlation was satisfactory in serum samples from 34 patients with M-proteins which had been detected by immunoelectrophoresis. In addition, a comparison of CZE electropherograms with those from CAE showed that small M-proteins that went undetected by CAE could be detected by CZE in four patients whose diseases included epipharyngeal carcinoma, solitary plasmacytoma, Crow-Fukase syndrome and macroglobulinemia. The improved resolution produced by a longer capillary may be effective for the detection of small M-proteins.     

Evaluation of the excretion of vanilmandelic acid using paper and cellulose acetate electrophoresis

The authors compare the results of vanillylmandelic acid (VMA) excretion measurements by high-voltage electrophoresis on paper and by microelectrophoresis on cellulose acetate. Transverse scanning of electrophoregrams has been used for quantitative evaluation of the results of microelectrophoregrams on cellulose acetate. The results of VMA excretion measurements by the two methods have been in good correlation: r = 0.93, n = 15, y = 0.17 + 0.78x, p less than 0.01. Electrophoresis on cellulose acetate is three times less labor consuming and can be performed with Soviet equipment and maintenance medium. The excretion intensity can be assessed visually by reference values of VMA concentration.     

Computer-supported interpretation of protein profiles after capillary electrophoresis

BACKGROUND: Electrophoretic patterns of proteins in serum/plasma are useful in the diagnosis and evaluation of many diseases. Capillary zone electrophoresis (CZE) allows rapid and automated protein separation and produces digital absorbance data, appropriate for mathematical analysis. We previously demonstrated success in detection of monoclonal immunoglobulins in such a system. This study tests new algorithms to produce rapid standardized computer-supported interpretation of the entire electropherogram. METHODS: Data from Beckman Paragon CZE 2000 electropherograms were compared with quantitative protein data from >800 routine clinical samples. Algorithms were designed to produce semiquantitative analyses of major proteins and to define different patterns of inflammation based on the electropherogram. RESULTS: The algorithms produced reliable semiquantitative evaluations of prealbumin, albumin, alpha1-antitrypsin, haptoglobin, and transferrin, but were less accurate for alpha1-acid glycoprotein. Some genetic variants of albumin and deficiency variants of alpha1-antitrypsin were easily recognized. Complex clinical traits such as degree and type of inflammation could be evaluated. When used together with previously developed algorithms addressing immunoglobulins, the new algorithms provide relevant clinical interpretation. Selected outputs indicate the need for reflex testing or evaluation by specialists. CONCLUSIONS: Automation of both electrophoresis and interpretation can provide a rapid, inexpensive, standardized analysis that can hopefully improve the diagnostic information and clinical outcome for large groups of patients. It also provides objective criteria for clinical interpretations, to be validated or adjusted in future clinical studies.     

Precision and long-term stability of capillary electrophoresis measurement of serum protein zones

BACKGROUND: Analytical evaluations of an available system for capillary zone electrophoresis (CZE) of serum protein have been reported. However, data concerning long-term precision and stability of the system, operated under routine conditions, are lacking. We report data from an internal quality control (QC) scheme, obtained over a 1-year period. METHODS: Measurements were done with a pair of instruments (Beckman Paragon CZE 2000 system), each equipped with seven capillaries. After preliminary (1 month) assessment of possible inter-capillary and inter-instrument variations, the QC material (a home prepared serum pool stored in the frozen state) was assayed daily over a 1-year period. RESULTS: Maximum inter-capillary and inter-instrument differences were 3.1% and 2.4%. No significant trend was observed for daily values (205 measurements over 1 year); in the same period overall imprecision values (CV) were in the interval 1.2% (albumin) to 3.2-6.1% (globulin zones). Mean monthly imprecision (CV) values were in the interval 1.1% (albumin) to 5.2% (globulin zones). There was no significant trend of monthly means with time. The observed imprecision values were within the biological variation-derived goals for imprecision. CONCLUSIONS: It is concluded that the assessed analytical instruments, operated in routine conditions, show long-term stability and imprecision consistent with the clinical use of the results produced.     

Measurement of serum monoclonal components: comparison between densitometry and capillary zone electrophoresis.

Quantitative measurement of serum monoclonal protein (M-protein) is one of the most important tools for monitoring disease activity in monoclonal gammopathies. The aims of this study were to evaluate serum M-protein quantification by capillary zone electrophoresis (CZE) and to compare results with those obtained by densitometric scanning of high-resolution agarose gel electrophoresis (HRE-AGE). The evaluation was carried out on 82 samples from patients with various monoclonal gammopathies. All the suspected M-proteins were confirmed and characterised by immunofixation on agarose gel (IFE). CZE was performed on a Paragon CZE 2000 system (Beckman Coulter). Passing-Bablok regression was: y (CZE)=1.27 x(HRE-AGE)-5.21 g/L. The correlation coefficient was 0.92. Bland-Altman analysis demonstrated a mean difference of -1.83 g/L (95% CI -0.76 to -2.90) with clear evidence of a concentration-related bias. Densitometry gave higher values at low M-spikes (<20 g/L), whereas CZE gave higher values at large M-spikes (>20 g/L). The concentration-related bias was found to be independent of the immunoglobulin isotype. In conclusion, to compare previous results obtained by M-protein densitometric scanning with those obtained by direct measurement of CZE peaks, the calculation of a univocal transforming factor appears to be unreliable.     

Imprecision of quantification of serum protein fractions by electrophoresis on cellulose acetate

We studied the precision of densitometric quantification of the protein zones resolved by cellulose acetate electrophoresis. Replicate analyses of patients' samples by a single technologist showed mean CVs ranging from 2.9% for serum albumin to 9.5% for alpha 1-globulin. There were marked differences in measurements obtained by replicate analysis of the same samples by two experienced technologists. We calculated what changes in fractional concentrations would be analytically significant and concluded that densitometry of cellulose acetate electrophoretograms can only be semi-quantitative. We suggest that visual interpretation of high-resolution electrophoretic patterns by a trained observer can replace densitometry in most cases.     

Ultraviolet-absorbing organic anions in uremic serum separated by capillary zone electrophoresis, and quantification of hippuric acid

Organic anions accumulated in blood serum of patients with chronic renal failure were separated by a novel technique: closed-system capillary zone electrophoresis (CZE) in a pH6 carrier-electrolyte system. Hippuric acid (HA), p-hydroxyhippuric acid, and uric acid were identified by their co-elution with standards prepared in ultrafiltered normal serum and by comparison with the corresponding ultraviolet-detected peaks positively identified in the HPLC analyses. Analysis time for the entire profile is 8 min. Repeatabilities (CVs) of CZE migration times and peak areas of the three acids in serum samples were about 0.7% and 6%, respectively. We quantified HA in 10 ultrafiltered uremic serum samples and compared results with those by a previously described HPLC procedure. The very good agreement further supports the identification of hippuric acid. Accuracy and precision of the CZE method were similar to those for the HPLC gradient-elution method, but analysis time for HA (8 min) is much less than by HPLC (90 min). Our technique is very suitable for selective, rapid analysis for (ultraviolet-absorbing) anionic constituents in ultrafiltered uremic serum, without any sample pretreatment.     

应用高效毛细管电泳筛检和鉴定血清中M蛋白

目的:应用毛细管区带电泳法(CZE)和毛细管区带电泳-免疫削减法(IS-CZE)对M蛋白进行筛检和鉴定。方法:运用CZE和琼脂糖凝胶电泳(AGE)分别对532例血清进行M蛋白的筛检;用IS-CZE和免疫固定电泳(IFE)对M蛋白阳性的64例标本进行免疫分型。结果:与AGE相比较,CZE筛检M蛋白的阳性率为96.9%;与IFE相比较,IS-CZE分型的符合率为89.1%;自包被固相抗体能满足试验要求。结论:毛细管区带电泳可高效、快速完成M蛋白的筛检和鉴定,适合临床推广。     

"Fragmented" isoenzymes of alkaline phosphatase in the diagnosis of transient hyperphosphatasemia

We describe the appearance of "fragmented" isoenzymes of serum alkaline phosphatase (EC 3.1.3.1) in two cases of transient hyperphosphatasemia. We determined the isoenzymes by liquid chromatography, then characterized them by heat inactivation, inhibition with 5 mmol/L L-phenylalanine solution, and electrophoresis on cellulose acetate membranes. We suspect that a virus-induced decrease in clearance of the enzyme from serum is responsible for a similar increase of bone and liver isoenzyme activities and for the presence of these fragmented isoenzymes in transient hyperphosphatasemia.     

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 CEofix(TM)-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.     

A study of the interaction of bromocresol green with isolated serum globulin fractions

Electrophoretically isolated globulin fractions from normal and abnormal sera have been allowed to react with the bromocresol green (BCG) reagent as used for the determination of serum albumin. The α- and β-globulin fractions were found to react with BCG producing significant “albumin” peaks using a continuous automated method. The γ-globulin fraction did not react with the BCG reagent. Immunoprecipitation techniques were used to establish that the isolated globulin fractions did not contain significant amounts of contaminating albumin. The results from this study cast considerable doubt upon the specificity of BCG for albumin and explain the discrepancy between the BCG method and a cellulose acetate electrophoresis technique in the determination of low albumin levels in abnormal sera.     

Solid phase immunoassay for high molecular weight alkaline phosphatase in human sera using a specific monoclonal antibody

A murine hybridoma producing monoclonal antibody (MoAb HMAP-1) to human high molecular weight alkaline phosphatase (HMAP) was derived using enzyme partially purified from human serum as the immunogen. The antibody did not cross-react with the liver, bone, intestinal or placental isozymes of alkaline phosphatase (AP), and did not react with AP in bile. A monoclonal antibody immunocatalytic assay for HMAP in serum was developed using MoAb HMAP-1 bound to nitrocellulose membrane discs. The method was rapid and reproducible, giving good correlation with results from cellulose acetate membrane electrophoresis and having the added advantages of increased sensitivity and specificity. A large number of sera can now be assayed to evaluate the significance of serum HMAP in relation to other AP activities and to the differential diagnosis of liver disease.     

Measurement uncertainty in laboratory reports: A tool for improving the interpretation of test results

BackgroundMeasurement uncertainty (MU) estimation has been introduced by ISO 15189 for the accreditation of clinical laboratories. Although MU reporting is not required, its inclusion in medical reports is of potential assistance to physicians in results interpretation.MethodsMU reporting was evaluated with respect to different test purposes, namely comparison with reference intervals (RI), patient monitoring or comparison with clinical decision limits. Clinical Biochemistry, Hematology, Coagulation and Clinical Immunology measurands were used as examples. Assuming Gaussian RI distribution, the probability of retesting due to MU was determined by simulations. Significant MU variations were compared against the reference change value (RCV) and clinical decision limits.ResultsThree potential scenarios emerged for RI. For 12 measurands, depending on the MU interval, a potential change in results interpretation was found only for Sodium and S-Protein. On considering only the results within RI, simulations confirmed that up to 8.6% of MU intervals encompassed the RI limits, thus potentially leading to retesting. For tests used in patient monitoring, significant MU variations were comparable to those calculated by RCV, with the exception of CEA. For tests results evaluated with respect to clinical decision limits, on including MU, the clinical interpretation may be improved (e.g. for tPSA).ConclusionThe findings made in the present study, which considers real MU data and hypothetical results obtained for a series of measurands, support the concept that MU may aid the physician's interpretation thus ensuring reliable clinical decision making.     

Analytical evaluation of a new capillary electrophoresis method for carbohydrate-deficient transferrin measurement

BACKGROUND: Carbohydrate-deficient transferrin (CDT), the sum of a- and disialotransferrin, is considered the most efficient routine biological marker of alcohol abuse. In recent years, methods based on capillary zone electrophoresis (CZE) have been developed using specialized monocapillary systems. These are characterized by a high analytical detection level, counterbalanced by a poor productivity. We evaluated a new CZE method for CDT measurement on the Sebia Capillarys, an eight-capillary system developed for routine serum capillary electrophoresis. METHODS: Precision and possible biases due to abnormal (low or high) transferrin levels or lipemic samples were assessed. Exactitude and precision were tested by comparison with a HPLC procedure acknowledged to be the most reliable to date. The validity of the manufacturer's cut-off was checked by measuring CDT in a population comprising abstaining patients, moderate alcohol consumers and alcohol abusers. Lastly, the method was compared to the routine %CDT TIA and N Latex CDT methods. RESULTS: The imprecision was 18.5% at the minimum detection level and decreased to 6.1% for high CDT values. No significant shift in the CDT results was observed in relation to abnormally low or high serum transferrin, or in lipemic samples. A high level of concordance was observed with the HPLC method used as reference. The results were strongly correlated with both other routine methods (r>0.90). The diagnostic values were comparable to the literature data, even if differences in the studied populations make difficult a direct comparison of the results. Our data suggested that the cut-off could be raised from 1.3% to 1.4% to reduce the number of false positive values without loss of diagnostic efficiency. CONCLUSIONS: This Capillarys method from Sebia showed good precision as compared to those published using other CZE methods. Capillarys method correlated well with HPLC and two routine methods. However, we noticed significant bias at low CDT concentrations. Therefore, with the advantage of high throughput and full automation, these results indicate that the new method is a consistent alternative to the other methods proposed for routine CDT measurement.     

Effect of ampicillin-sulbactam on clinical capillary zone electrophoresis of serum proteins

BACKGROUND: Capillary zone electrophoresis (CZE) is a well-accepted automated method used to separate serum proteins and detect monoclonal components. CZE uses ultraviolet detection at 214 nm to directly quantify proteins via peptide bonds. Any substance that absorbs at 214 nm and is present in serum can potentially interfere with CZE analysis. This has been reported for radio-contrast media and antibiotics. METHODS: Here we describe a peak on the anode side of the alpha(2)-globulin fraction caused by the antibiotic ampicillin-sulbactam (Unacid). RESULTS AND CONCLUSIONS: Extra peaks that can be misinterpreted as monoclonal components can be present in almost all electrophoretic fractions of CZE. Immunosubtraction or immunofixation is always required to rule out these conditions.     

Computer-supported detection of M-components and evaluation of immunoglobulins after capillary electrophoresis

BACKGROUND: Electrophoresis of serum samples allows detection of monoclonal gammopathies indicative of multiple myeloma, Waldenstr?m macroglobulinemia, monoclonal gammopathy of undetermined significance, and amyloidosis. Present methods of high-resolution agarose gel electrophoresis (HRAGE) and immunofixation electrophoresis (IFE) are manual and labor-intensive. Capillary zone electrophoresis (CZE) allows rapid automated protein separation and produces digital absorbance data, appropriate as input for a computerized decision support system. METHODS: Using the Beckman Paragon CZE 2000 instrument, we analyzed 711 routine clinical samples, including 95 monoclonal components (MCs) and 9 cases of Bence Jones myeloma, in both the CZE and HRAGE systems. Mathematical algorithms developed for the detection of monoclonal immunoglobulins (MCs) in the gamma- and ss-regions of the electropherogram were tested on the entire material. Additional algorithms evaluating oligoclonality and polyclonal concentrations of immunoglobulins were also tested. RESULTS: CZE electropherograms corresponded well with HRAGE. Only one IgG MC of 1 g/L, visible on HRAGE, was not visible after CZE. Algorithms detected 94 of 95 MCs (98.9%) and 100% of those visible after CZE. Of 607 samples lacking an MC on HRAGE, only 3 were identified by the algorithms (specificity, 99%). Algorithms evaluating total gammaglobulinemia and oligoclonality also identified several cases of Bence Jones myeloma. CONCLUSIONS: The use of capillary electrophoresis provides a modern, rapid, and cost-effective method of analyzing serum proteins. The additional option of computerized decision support, which provides rapid and standardized interpretations, should increase the clinical availability and usefulness of protein analyses in the future.     

A practicable two-dimensional electrophoretic method for routine analysis of urinary proteins

A two dimensional electrophoretic method is described for the routine clinical analysis of urinary proteins. Cellulose acetate electrophoresis is used for the first dimension, and SDS (sodium dodecyl sulphate) electrophoresis for the second dimension, the latter being performed together with gel staining (Coomassie Blue) on the "Phast System". The separation media are supplied as "ready-to-use" materials. The method is reliable and reproducible, and is complete within 100 minutes. The resulting two-dimensional pattern of major proteinuria constituents is evaluated visually from the distribution according to molecular weight (second dimension) and from the five zone pattern of cellulose acetate electrophoresis (first dimension). Certain "marker" proteins specific for certain pathological changes, as well as certain characteristic changes in protein spot constellation, can be more easily recognized and evaluated than in one-dimensional SDS electrophoresis.     

From paper electrophoresis to computer-supported interpretation of capillary electrophoresis--clinical plasma protein analysis in Malm?, Sweden.

Protein analyses have been used in Malm? as a routine clinical diagnostic tool since 1953. Most serum samples are submitted for "protein profiles" including capillary zone electrophoresis and rate immune nephelometric quantification of nine proteins (five in urines), although analysis of single proteins may be requested. Standardization between laboratories in our region has been greatly improved by automation, CRM 470 calibration and external quality assurance. We are further extending standardization by developing computer supported interpretations using a program with improved user interface and graphical representation of electrophoretic curves superimposed upon a shaded reference interval. Programming is underway to provide complete automatic interpretation of these curves. Together, capillary electrophoresis (with access to mathematical analysis) and immunochemical quantifications allow a highly automated process accessible to further digital analysis and automated interpretation. Rapid, cost-effective and standardized analysis of serum protein profiles should improve the diagnostic evaluation of many categories of patients.     

Comparative study of lipoproteinograms obtained by three different methods (author's transl)

Comparative study of lipoproteinograms obtained by three different methodsA comparison of the lipoproteinograms of 234 normal sera obtained by electrophoresis on albuminous paper, cellulose acetate gel and agar-agar enables the normal values of each method to be defined, as well as the limits of the pathological character given to the prebetalipoproteins by Fredrickson's classification. We find one group of subjects whose sera show no prebetalipoproteins, even by the most sensitive method.