The Application of Clinical and Molecular Diagnostic Techniques to Identify a Rare Haemoglobin Variant

Haemoglobin disorders represent a heterogeneous group of inherited conditions that involve at least one genetic abnormality in one or more of the globin chains, resulting in changes in the structure, function, and/or amount of haemoglobin molecules, which are very important for their related clinical aspects. Detecting and characterizing these disorders depends primarily on laboratory methods that employ traditional approaches and, when necessary, newer methodologies essential for solving a number of diagnostic challenges. This review provides an overview of key laboratory techniques in the diagnosis of haemoglobinopathies, focusing on the challenges, advancements, and future directions in this field. Moreover, many haemoglobinopathies are benign and clinically silent, but it is not uncommon to find unexpected variants during routine laboratory tests. The present work reported a rare and clinically interesting case of identification of haemoglobin fractions in an adult man by the determination of glycated haemoglobin (HbA1c) during a routine laboratory assessment, highlighting how the correct use of laboratory data can modify and improve the patient's clinical management.

An efficient isoelectric focusing of microcolumn array chip for screening of adult Beta-Thalassemia

Traditional capillary isoelectric focusing (cIEF), liquid chromatography (LC) and capillary zone electrophoresis (CZE) still suffered from low resolution for hemoglobinopathy screening. Herein, a 30-mm pH 5.2-7.8 microcolumn IEF (mIEF) array chip was developed for hemoglobinopathy screening. As a proof of concept, adult beta-thalassemia was chosen as a model disease. In the method, blood samples were hemolyzed via hemolysin solution and loaded into the microcolumn. The experiments showed that (i) the species of Hb A, F, A₂ and variants were clearly separated in the chip, and the resolution was greatly higher than the ones of LC/CZE/cIEF; (ii) up to 24 samples could be simultaneously analyzed in 12-min run; (iii) the intraday and interday RSDs were respectively 3.32-4.91 % and 4.07-5.33 %. The assays of mIEF to total 634 samples were compared with the ones of LC (n = 327) and PCR (n = 307). The cutoff of 3.5 % HbA₂ led to the sensitivity of 100 % and specificity of 89.1 % for the mIEF-based screening; and there was 96.7 % coincidence between the methods of mIEF and PCR if refer Hb A₂ and F. The method had the merits of facility, efficiency, specificity and sensitivity in contrast to the currently-used methods, implying its potential to screening of beta-thalassemia and hemoglobinopathies.

An Overview of CE in Clinical Analysis

The development and general applications of capillary electrophoresis (CE) in the field of clinical chemistry are discussed. It is shown how the early development of electrophoresis was closely linked to clinical testing. The rise of gel electrophoresis in clinical chemistry is described, as well as the eventual developments that lead to the creation and the use of modern CE. The general principles of CE are reviewed and the potential advantages of this method in clinical testing are examined. Finally, an overview is presented of several areas in which CE has been developed and is currently being explored for use with clinical samples.

Advances in detection of hemoglobinopathies

Hemoglobin disorders are recognized as one of the most common inherited diseases worldwide. Detecting and characterizing variant hemoglobins and thalassemias depends primarily on clinical laboratory methods. Multiple biophysical, biochemical, and genetic assays are available to provide phenotypic or genotypic evidence of pathology. For many years conventional slab-gel electrophoresis and HPLC were the most commonly utilized laboratory methods. However, the field has rapidly expanded to regularly include capillary zone electrophoresis, molecular assays, and, more recently, mass spectrometric assays. Interpretation of these techniques is, in general, complicated because of the involvement of multiple polymorphic genes. Proper characterization of hemoglobin variants is necessary for diagnosis, primary prevention and genetic counseling for underlying disorders. This review provides an overview of the current hemoglobin analysis techniques, and also discusses technologies that have potential to translate into widespread clinical settings.

Expression of hemoglobin variant migration by capillary electrophoresis relative to hemoglobin A2 improves precision

We report the precision of the mean migration position of hemoglobin (Hb)S, HbC, HbG (Philadelphia), and HbD (Los Angeles) in 193 samples of whole blood assayed by capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). By expressing the migration of Hb variants by CE relative to that of HbA(2) in the same sample, there was a significant improvement in the coefficient of variation for each variant studied. The potential usefulness of expressing Hb variants relative to that of HbA(2) was evaluated by comparing the separation of 2 closely migrating Hbs. When expressed by their initial migrations on CE, 25 of the 43 cases of HbG and HbD overlapped. However, when the migrations of these variants were expressed relative to the HbA(2) in the same sample, the 24 cases of HbG separated completely from the 19 cases of HbD. These findings suggest that expressing Hb variants relative to an internal standard, such as HbA(2), may be of value for establishing a library of variant Hbs evaluated by CE.

The range of hemoglobin A(2) in hemoglobin E heterozygotes as determined by capillary electrophoresis

Capillary electrophoresis (CE) is capable of distinguishing hemoglobin E (HbE) from hemoglobin A(2) (HbA(2)), thus permitting quantification of HbA(2) in patients with HbE. In this study, routine samples submitted for evaluation of hemoglobinopathy that demonstrated HbE were studied by high-pressure liquid chromatography and CE. The data for 52 samples from adult HbE heterozygotes were compared with those for a control group consisting of 209 patients. The mean HbA(2) of patients with HbE trait was 3.4% (SD, 0.4%), which was significantly higher (P < .001) than the 2.6% (SD, 0.4%) for the control group. Seven samples from adults homozygous for HbE were also evaluated. The mean HbA(2) of HbE homozygotes was 4.4%, which was significantly greater (P < .001) than the HbA(2) values for the HbE heterozygotes. Data from these cases provide an estimate of the range of HbA(2) in patients with HbE when evaluated by CE.

Quantification of HbA(2) in patients with and without beta-thalassemia and in the presence of HbS, HbC, HbE, and HbD Punjab hemoglobin variants: comparison of two systems

We studied whether problems quantifying hemoglobin A(2) (HbA(2)) could be resolved by using capillary electrophoresis. HbA(2) was quantified on whole blood samples from patients with and without beta-thalassemia trait and patients heterozygous for HbE, HbS, HbC, and HbD Punjab using the VARIANT II beta-thalassemia (Bio-Rad, Hercules, CA) and Capillarys 2 (Sebia, Norcross, GA). HbA(2) results in patients with and without beta-thalassemia trait were lower with the Capillarys 2 system. Reasonable HbA(2) results were obtained for patients with HbD Punjab and HbE traits on the Capillarys 2. HbA(2) results for patients with HbS, heterozygous and homozygous, were similar by both methods. Interference due to coelution for HbA(2) results for patients with HbC trait was noted on the Capillarys 2. Between-day imprecision on the VARIANT II is less than that for the Capillarys 2 system. The Capillarys 2 is superior to the VARIANT II for quantifying HbA(2) in the presence of HbE and HbD Punjab traits. The Capillarys 2 offers only slight advantages over the VARIANT II for quantifying HbA(2) in the presence of heterozygous and homozygous HbS. The Capillarys 2 gives inferior HbA(2) results for patients with HbC trait.

CE-based analysis of hemoglobin and its applications in clinical analysis

This review focuses on the developments and trends in CE including CIEF, CZE, MEKC, two-dimensional conjunction of CIEF-capillary gel electrophoresis, and MEKC-CZE on microfluidic devices coupled to different detection approaches, such as UV absorbance, LIF, MS, and chemiluminescence etc. for performing analysis of hemoglobin (Hb), also with an emphasis on its applications in clinical analysis. Analysis of human Hb is of important clinical sense for numerous hemoglobinopathies associated with the congenital defects and abnormal contents of Hb. The diversiform modes render CE a comprehensive primary clinical tool for Hb analysis, which is rapid, sensitive, high-resolution, and not labor-intensive.

Evaluation of a new Sebia kit for analysis of hemoglobin fractions and variants on the Capillarys system

We evaluated the analytical performances of the new Sebia kit for quantification of hemoglobin fractions (HbA, HbF and HbA2) and structural hemoglobin variants on the Capillarys system. This automated capillary zone electrophoresis method uses an alkaline buffer with silica capillaries and spectrophotometric detection. Specimen stability was evaluated during 1 month. The reproducibility of migration and the imprecision of quantification were also investigated. Comparison with the Beckman P/ACE system was performed on 202 samples. A total of 131 subjects without any hematological abnormality were analyzed to establish the HbA2 reference ranges based on our local population. Quantification of the Hb fractions and variants exhibited excellent stability for 4 weeks of storage at 4 degrees C, with CVs < 0.3%. The imprecision of the migration normalized to that of HbA2 for all hemoglobins tested (fractions and variants) was low, with a CV of < 2.5%. At physiological and pathological levels, total imprecision ranged from 1.9% to 4.6% for HbA2, from 0.6% to 9.7% for HbF, and from 0.6% to 1% for HbS. Statistical analysis revealed a small proportional negative bias for HbA2 (-8.6%). Small systematic bias (-0.2%) and proportional bias (-28%) were observed for HbF. No statistically significant difference was found for HbS. The reference range for HbA2 was 2.1-3.2%. The Capillarys system is a fully automated and accurate system that gives high-resolution performance and displays appropriate characteristics for use as a routine method for the diagnosis of thalassemias and hemoglobinopathies.

Capillary electrophoresis of hemoglobin

Capillary electrophoresis (CE) has been used in a variety of in-house capillary isoelectric focusing (CIEF) and capillary zone electrophoresis (CZE) assays for the detection of hemoglobin (Hb) variants and the quantitation of HbA2 and HbF. A commercial kit has also been produced for the analysis of hemoglobin variants and thalassemia screening. Though CE methods have been shown to be able to detect many variants, final identification of the variant needs specialized testing such as DNA technology. Over the past 2 years, many instruments that had been used for these hemoglobin variant screening and thalassemia assays have been withdrawn from sale. Although CE HbA1c analysis is available, it cannot compete in turnaround time or cost with automated HPLC commercial instruments that give accurate HbA1c results in 3 or 4 minutes. Hence we do not anticipate a bright future for the analysis of hemoglobin by CE.

Is capillary electrophoresis a method of choice for systematic toxicological analysis?

This review presents an overview of current research on the use of capillary electrophoretic techniques for the analysis of drugs in biological matrices. The discussion focuses on the applicability of the methods for the identification of unknown toxic compounds, which is defined as systematic toxicological analysis (STA). The aim is to establish whether or not capillary electrophoresis (CE), in one or more of its separation modes, is a method of choice in systematic toxicological analysis. To answer this question, various aspects are discussed, including sample work-up, separation modes, detection techniques, electrophoretic concentration, and identification by database retrieval. Several ways to improve the poor reproducibility and sensitivity are discussed. This leads to the conclusion that CE can be comparable to HPLC in those respects, while it is more favorable in speed, efficiency, and cost. Thus, we conclude that CE is a method of choice for STA, keeping in mind that every method has its limitations and that a combination of several non-correlated methods is always required for the identification of unknown compounds.

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.

Enhanced pharmaceutical analysis by CE using dynamic surface coating system

The poor repeatability of migration times in capillary electrophoresis (CE) within an injection sequence and between capillaries can be a difficulty when implementing CE for routine pharmaceutical analysis. The use of a dynamic surface coating has been shown to improve the routine performance of CE. The surface coating generates an appreciable electro-osmotic flow at low pH, which reduces analysis times for basic drugs compared to the low pH buffers typically used in CE. The repeatability of migration times and repeatability of migration times between capillaries was improved. Peak tailing for basic drugs was also reduced which improved peak shapes and peak area integration precision. It is concluded that the dynamic coating system is a positive advance in the routine implementation of CE into pharmaceutical analysis.

Advances ofcapillary electrophoresis in clinical and forensic analysis (1999-2000)

In this paper, capillary electrophoresis in clinical and forensic analysis is reviewed on the basis of the literature of 1999, 2000 and the first papers in 2001. An overview of progress relevant examples for each major field of application, namely (i) analysis of drug seizures, explosives residues, gunshot residues and inks, (ii) monitoring of drugs, endogenous small molecules and ions in biofluids and tissues, (iii) general screening for serum proteins and analysis of specific proteins (carbohydrate deficient transferrin, alpha1-antitrypsin, lipoproteins and hemoglobins) in biological fluids, and (iv) analysis of nucleic acids and oligonucleotides in biological samples, including oligonucleotide therapeutics, are presented.