Evaluation of a capillary zone electrophoresis system versus a conventional agarose gel system for routine serum protein separation and monoclonal component typing

Capillary zone electrophoresis of serum proteins is increasingly gaining impact in clinical laboratories. During 2003, we compared the fully automated capillary electrophoresis (CE) system from Beckman (Paragon CZE 2000) with the method agarose gel electrophoresis Sebia (Hydrasis-Hyris, AGE). This new study focused on the evaluation of analytical performance and a comparison including 115 fresh routine samples (group A) and a series of 97 frozen pathologic sera with suspicion of monoclonal protein (group B). Coefficients of variation (CVs %) for the five classical protein fractions have been reported to be consistenly < 9% in within-run and < 10% in between-run imprecision studies with the Paragon 2000 system. The results of the comparison study (group A) demonstrated a good correlation between the CE system and AGE, except for beta-globulin (r = 0.65). Among the 97 pathologic serum samples (group B), there were 90 in which we detected a monoclonal protein by immunofixation (IF) (immunosubtraction (IS) was not used). AGE and Paragon 2000 failed to detect 7 and 12 monoclonal proteins, respectively, leading to a concordance to 92% for AGE and 87% for Paragon 2000 for identifying electrophoretic abnormalities in this group. Beta-globulin abnormalities and M paraprotein were well detected with Paragon 2000. Only 81% (21 vs 26) of the gammopathies were immunotyped with IS by two readers blinded to the IF immunotype. The Paragon 2000 is a reliable alternative to conventional agarose gel electrophoresis combining the advantages of full automation (rapidity, ease of use and cost) with high analytical performance. Qualified interpretation of results requires an adaptation period which could further improve concordance between the methods. Recently, this CE system has been improved by the manufacturer (Beckman) concerning the migration buffer and detection of beta-globulin abnormalities.     

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.     

Separation of serum proteins by automated capillary zone electrophoresis.

Capillary zone electrophoresis (CZE) of serum proteins is increasingly gaining impact in clinical laboratories. Two automated multichannel instruments dedicated to the separation of serum proteins have become available over the last 6 years, the Paragon CZE 2000 (Beckman Coulter, CA, USA) and, more recently, the Capillarys (Sebia, France). This review focuses on the performance of these commercial instruments to separate serum proteins in a clinical laboratory setting. The utility of CZE to recognize various dysproteinemias and to detect and identify monoclonal proteins will be described and systematically reviewed. The reader will be provided with a summation and an understanding of CZE-specific interference.     

Evaluation of a new capillary zone electrophoresis system for the identification and typing of Bence Jones Protein

OBJECTIVES: Capillary electrophoresis has recently emerged as a new sensitive technique for the separation of urinary proteins. We evaluated a new method for Bence Jones Protein (BJP) detection and characterization on native urine samples by the Paragon CZE 2000 system. To avoid interference in electrophoretic separation, urine samples were preliminarily treated for the selective removal of interfering salt particles. DESIGN AND METHODS: The evaluation was done on a total of 350 fresh 24-h urine samples. The salt particle removal consisted of a manual chromatographic separation, optimized in the course of our evaluation. Capillary zone urinary protein electrophoresis (CZ-UPE) was compared with conventional high-resolution electrophoresis on an agarose gel, while capillary immunosubtraction (CZU-IFE) was compared with agarose gel immunofixation. RESULTS: After finding a consistent protein loss in eluates, the preanalytical treatment was optimized by changing sample dilution and eluate collection. The within- and between-run imprecision values for monoclonal peaks corresponding to BJP ranged from 0.4-12.2% to 3.3-6.3%, respectively. The detection limit for BJP, defined as the lowest measurable monoclonal peak on CZ-UPE, was 0.0012 g/L for kappa BJP and 0.0007 g/L for lambda BJP. CZ-UPE and CZU-IFE sensitivities were significantly lower in urine samples with a total protein level < or = 100 mg/L (67% and 78%, respectively) compared to those with total protein >100 mg/L (92% and 94%, respectively). Comparison between BJP measurements obtained from densitometric scanning with those from absorbance tracing showed a correlation coefficient of 0.994 and a bias of 29.8 mg/L. CONCLUSIONS: Paragon CZE 2000 can be introduced in routine for screening and typing of BJP; in urine samples with a total protein level >100 mg/L, the performance is consistent with results from published validation studies on CZE applied to serum samples.     

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.     

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。     

Linearity and detection limit in the measurement of serum M-protein with the capillary zone electrophoresis system Capillarys.

We studied the linearity and detection limits of the capillary zone electrophoresis system Capillarys in the measurement of serum monoclonal protein. Three monoclonal proteins with different isotypes and electrophoretic migrations were diluted with a hypo-gamma-globulinemic polyclonal serum pool. Mathematical linearity was observed for all monoclonal protein isotypes in the ranges studied without removing the polyclonal gamma-globulin background. Theoretical concentrations of 0.43, 0.89 and 0.33 g/L for monoclonal proteins immunoglobulin (Ig)G, IgA and IgM, respectively, gave a discernible spike by Capillarys, although they were measured as 0.76, 1.09 and 0.76g/L, respectively. We observed overestimation of monoclonal protein inversely correlated to concentrations below 15 g/L. All these limitations have to be taken into account when monitoring monoclonal proteins, because the loss of linearity and the protein background may hide an increase in concentration at low levels.     

Atypical findings of protein studies using capillary zone electrophoresis.

We present two atypical cases of protein studies that were evaluated by immunofixation and immunosubtraction using capillary zone electrophoresis and high-resolution agarose gel electrophoresis. The first study showed an abnormal peak in the beta region by capillary zone electrophoresis that was located in the gamma region of the high-resolution agarose gel electrophoresis. Further investigation showed that this monoclonal protein was displaced due to binding with beta-lipoproteins. In the second case, a large peak was detected in the alpha-2 region and was shown by capillary zone electrophoresis to be a non-proteinaceous material that mimicked a paraprotein.     

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.     

Automated multicapillary electrophoresis for analysis of human serum proteins

BACKGROUND: We evaluated a new, automated multicapillary zone electrophoresis (CE) instrument (Capillarys), 4.51 software version; Sebia) for human serum protein analysis. METHODS: With the Capillarys beta1-beta2+ reagent set, proteins were separated at 7 kV for 4 min in 15.5 cm x 25 micro m fused-silica capillaries (n = 8) at 35.5 degrees C in a pH 10 buffer with online detection at 200 nm. Serum samples with different electrophoretic patterns (n = 265) or potential interference (n = 69) were analyzed and compared with agarose gel electrophoresis (AGE; Hydrasys)-Hyrys, Hydragel protein(e) 15/30 reagent set; Sebia). RESULTS: CVs were <3.5% for albumin, <11% for alpha(1)-globulin, <4.1% for alpha(2)-globulin, <7.4% for beta-globulin, and <5.8% for gamma-globulin (3 control levels); measured throughput was 60 samples/h. In patients without paraprotein (n = 116), the median differences between CE and AGE were -5.4 g/L for albumin, 4.0 g/L for alpha(1)-globulin, 0.7 g/L for alpha(2)-globulin, 0.6 g/L for beta-globulin (P <0.001 for all fractions), and -0.1 g/L for gamma-globulin (not significant). More samples had at least one gamma-migrating peak detected by CE (n = 135 vs 130; paraprotein detection limit, approximately 0.5-0.7 g/L), but fewer were quantified (n = 84 vs 91) because of gamma- to beta-migration shifts. There was a 1.2 g/L median difference between CE and AGE for gamma-migrating paraprotein quantification (n = 69; P <0.001). Several ultraviolet-absorbing substances (lipid emulsion, hemoglobin) or molecules (contrast agent, gelatin-based plasma substitute) induced CE artifacts. CONCLUSIONS:The Capillarys instrument is a reliable CE system for serum protein analysis, combining advantages of full automation (ease of use, bar-code identification, computer-assisted correction of alpha(1)-globulins) with high analytical performances and throughput.     

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.     

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.     

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.     

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.     

Performance evaluation of the Helena V8 capillary electrophoresis system

ObjectivesTo compare the performance characteristics of the Helena V8® and Sebia CAPILLARYS2® automated capillary electrophoresis systems to agarose gel serum protein electrophoresis (SPE) and immunofixation electrophoresis (IFE) using the Helena SPIFE3000®.Design and methodsSerum protein electrophoresis and immunosubtraction was performed on 100 consecutive patient samples comparing two capillary-electrophoresis platforms with agarose-gel SPE and IFE; IFE was used as the gold standard. Chart review was performed on patients where results were discordant between methods. Analytical precision was determined using Sebia's normal and abnormal controls.ResultsThe sensitivities of the CAPILLARYS2, V8, and SPIFE3000 agarose gel for identification of monoclonal gammopathies were respectively 97.4 (95%CI 91.1–100), 92.3 (95%CI 82.2–100), and 89.9 (95%CI 79.1–97.6). The specificities of the CAPILLARYS2, V8, and SPIFE3000 agarose gel were respectively 57.6 (95%CI 45.0–70.2), 72.2 (95%CI 61.0–83.3), and 75.4 (95%CI 60–82.8). These analytical performance characteristics were statistically equivalent between systems (P > 0.05). The analytical precision of the capillary-based methods was also statistically equivalent. Chart review of available data from discordant samples revealed that 7/10 patients had a history of multiple myeloma or known monoclonal gammopathy and were being treated or monitored. All discordant samples had low concentration monoclonal proteins (< 0.3 g/dL). Both capillary-based methods performed poorly (collectively < 50% accuracy) at detecting low concentration non-IgG antibodies (IgA, IgM, and light chain monoclonal gammopathies) compared to IFE.ConclusionsThe Helena V8 and Sebia CAPILLARYS2 were analytically equivalent to the SIFE3000 for identification of IgG monoclonal gammopathies > 0.3 g/dL. Interpreters using the automated immunotyping/immunosubstraction systems performed poorly at detecting low concentration and non-IgG monoclonal gammopathies.     

28例多发性骨髓瘤的血清免疫学分析

目的　探讨多发性骨髓瘤(multiplemyeloma,MM)的血清免疫学特征。　方法　对28例MM患者的血清进行琼脂糖凝胶电泳及电泳扫描,血清蛋白和免疫球蛋白定量,以及免疫固定电泳。　结果　27例(96.4%)MM患者血清蛋白电泳可显示M带,IgG型、IgM型多在γ区,IgA型多在β区。不同型别MM免疫固定电泳图谱各异,IgG、IgA、IgM和单纯游离轻链的比例分别为46.4%、21.4%、17.9%、10.7%。在轻链型别中,IgG、IgM类M蛋白以κ型为主,单纯轻链型以λ型为主。免疫球蛋白定量显示M蛋白所属免疫球蛋白部分显著增高,非M蛋白所属免疫球蛋白显著降低。　结论　通过上述四种免疫化学综合实验对MM进行免疫分型,可对MM作出准确的实验室诊断。     

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.     

Use of immunoglobulin heavy- and light-chain measurements compared with existing techniques as a means of typing monoclonal immunoglobulins

Using automated measurements of kappa and lambda light chains and IgG, IgA, and IgM, we assessed the utility of the kappa/lambda ratio and the heavy chain/light chain ratio in characterizing monoclonal immunoglobulins previously identified by sensitive electrophoresis on agarose gel and typed by immunofixation or immunoelectrophoresis. We examined 348 selected samples, of which 165 contained monoclonal components, finding that 93.4% were detected and 89% correctly typed by this approach. Eight samples were shown to contain monoclonal light chains that were not visible as bands on electrophoresis but demonstrated abnormalities of the kappa/lambda or heavy chain/light chain ratio.     

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.