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

Reliability of hemoglobin A2 value as measured by the Premier Resolution system for screening of β-thalassemia carriers

OBJECTIVES

Accurate quantification of hemoglobin (Hb) A2 is vital for diagnosing β-thalassemia carriers. This study aimed to assess the precision and diagnostic utility of HbA2 measurements using the new high-performance liquid chromatography (HPLC) method, Premier Resolution, in comparison to capillary electrophoresis (CE).

METHODS

We analyzed 418 samples, previously identified as A2A by CE, using Premier Resolution-HPLC. We compared the results, established correlations, and determined an optimal HbA2 cutoff value for β-thalassemia screening. Additionally, we prospectively evaluated the chosen cutoff value in 632 samples. Mutations in the β- and α-globin genes were identified using polymerase chain reaction (PCR) techniques and DNA sequencing.

RESULTS

HbA2 levels were consistently higher with Premier Resolution, yet there was a significant correlation with CE in all samples (bias, -0.33; r, 0.991), β-thalassemia (bias, -0.27; r, 0.927), and non-β-thalassemia carriers (bias, -0.36; r, 0.928). An HbA2 cutoff value of ≥4.0 % for β-thalassemia screening achieved 100 % sensitivity and 99.6 % specificity. Further validation yielded sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 97.3 , 99.8, 97.3, 99.8, and 99.7 %, respectively. We also identified a rare β-Hb variant, Hb La Desirade [HBB:c.389C>T], associated with β-thalassemia and co-inherited with a single α-globin gene.

CONCLUSIONS

The Premier Resolution HPLC is a reliable and accurate method for routine β-thalassemia carrier screening, aligning with existing CE methods.

Comparison of HbA2 Using High Performance Liquid Chromatography Versus Haemoglobin Capillary Zone Electrophoresis

Thalassemia is among the most common hereditary disorders in the world. Approximately 5% of the world's population are carriers of hemoglobinopathies, and 2.9% are carriers of beta thalassemia. Haemoglobin A2 (HbA2) constitutes less than 3% of the total hemoglobin (Hb) in adults, and the determination of Hb A2 levels is important to diagnose the beta thalassemia trait (BTT). In some cases, the level of HbA2 is not typically elevated, and some difficulties may arise in making the diagnosis. Cation exchange high-performance liquid chromatography (HPLC) and HbCZE (haemoglobin capillary zone electrophoresis) are considered acceptable methods to diagnose BTT, but these vary in their accuracy and cut-offs. In this study, we attempted to compare HbA2 values using two methods, HPLC and HbCZE, in 536 whole blood samples sent by physician-ordered hemoglobinopathy screening over two years. This included antenatal women, patients with anemia not responding to iron, and cases of familial screening where either a child or a sibling had been diagnosed with hemoglobinopathy or thalassemia. The performance characteristics of both machines were compared for the detection of the 5 most common hemoglobin variants: Hb A, HbF, HbS, Hb C, and HbE. On comparing the HbA2 values, the HPLC showed higher values for HbA2 as compared to HbCZE, while the HbF and HbS measurement agreement was good between both methods. Normal ranges and mean normal values of HbA2 differ between different methods and different manufacturers; hence, each institute using these machines should validate its cutoffs.

The accuracy of haemoglobin A2 measurements in the presence and absence of haemoglobin S

The quantification of haemoglobin A2 by high-performance liquid chromatography (HPLC) was compared with quantification by capillary electrophoresis for control subjects and patients with sickle cell trait or sickle cell anaemia. Significant differences were found, with estimated values being higher by HPLC for control subjects and higher by capillary electrophoresis for sickle cell trait and sickle cell anaemia patients. There is an ongoing need for improved standardisation and alignment of methods.

Discovery of a biomarker for β-Thalassemia by HPLC-MS and improvement from Proton Transfer Reaction - Parallel Ion Parking

β-thalassemia is a quantitative hemoglobin (Hb) disorder resulting in reduced production of Hb A and increased levels of Hb A₂. Diagnosis of β-thalassemia can be problematic when combined with other structural Hb variants, so that the separation approaches in routine clinical centers are not sufficiently decisive to obtain accurate results. Here, we separate the intact Hb subunits by high-performance liquid chromatography, followed by top-down tandem mass spectrometry of intact subunits to distinguish Hb variants. Proton transfer reaction-parallel ion parking (PTR-PIP), in which a radical anion removes protons from multiply charged precursor ions and produces charge-reduced ions spanning a limited m/z range, was used to increase the signal-to-noise ratio of the subunits of interest. We demonstrate that the δ/β ratio can act as a biomarker to identify β-thalassemia in normal electrospray ionization MS1 and PTR-PIP MS1. The application of PTR-PIP significantly increases the sensitivity and specificity of the HPLC-MS method to identify δ/β ratio as a thalassemia biomarker.

Missing Hb Q-India Peak in a Triple-Heterozygous Patient with Hb D-Punjab/Hb Q-India/β-Thalassemia Trait

Interpretation of variant hemoglobins (Hbs) can pose challenges. We describe a puzzling case with multiple variant Hb peaks that was solved by family studies. A 32-year-old female with anemia and jaundice underwent cation exchange high performance liquid chromatography (HPLC), which revealed near-absence of Hb A along with variant peaks in the D- and C-windows (78.9 and 13.3%, respectively) and normal range of Hb F. As the HPLC did not fit any known pattern, family screening was performed. Her mother was heterozygous for Hb D-Punjab (HBB: c.364G>C) and Hb Q-India (HBA1: c.193G>C) with the hybrid α^Q-India/β^D-Punjab eluting in the C-window on HPLC. Her sister had β-thalassemia (β-thal) trait, while her brother was heterozygous for Hb Q-India. In view of the family study results, the index case was interpreted as a double heterozygote for Hb D-Punjab and β-thal with coinherited Hb Q-India. The Hb Q-India peak [retention time (RT) 4.7 min.] was absent on her HPLC as there were no normal β-globin chains available to bind with the α^Q-India chains. To the best of our knowledge, such an HPLC pattern with a missing Q-India peak, despite having inherited the α^Q-India variant, has not been previously reported. This case illustrates the importance of family screening as an inexpensive and rapid method to resolve difficult and unusual HPLC patterns.

Unexpected discovery of hemoglobinopathy C/β° thalassemia

High performance liquid chromatography (HPLC) is the current method of choice for the detection of hemoglobinopathies and the quantification of A2 and fetal hemoglobin. We are describing a case where a double heterozygosity C/beta-thalassemia was fortuitously identified, during assaying HBA1c, by HPLC.

Hemoglobin A2 (HbA2) has a measure of unreliability in diagnosing β-thalassemia trait (β-TT)

INTRODUCTION

Detection of β-thalassemia trait or carriers (β-TT) depends significantly on an increase in Hemoglobin A₂ (HbA₂) levels, which is found at low levels (<3%) in normal healthy individuals and elevated levels (≥3.5%) in β-TT individuals. The study was designed to evaluate the reliability of the diagnostic parameter HbA₂ in the differentiation of β-TT and non-β-TT in Saudis.

METHODS

The widely used high performance liquid chromatography (Variant II Bio-Rad) was used to measure HbA₂ levels in blood. Sanger sequencing was used to screen the variation in globin genes (HBB, HBD, HBA1, and HBA2). All the study subjects were divided into βTT and non-βTT (wild) categories based on the presence or absence of HBB variations and further sub-divided into false positive, true positive, false negative, and true negative, based on HbA₂ values.

RESULTS

Out of 288 samples, 96 had HBB gene mutations. Of the 96 β-TT samples, sickle cell trait (SCT) samples (n = 58) were excluded, while the remaining (38 β-TT) were included in the detailed analysis: seven subjects with the HBB mutation had normal HbA₂ (<3%), and three were borderline (3.1-3.9%). The remainder (n = 28) had an elevated HbA₂ level (>4%). Based on HbA₂ analysis alone, both these groups would be incorrectly diagnosed as normal. Similarly, of the 189 non-β-TT samples, 179 had normal HbA₂, eight had borderline HbA₂, and two had a HbA₂ level above 4%. Based on HbA₂ analysis alone, borderline and >4% HbA₂ individuals, negative for β-TT, can be incorrectly diagnosed as carriers.

CONCLUSION

Given the percentage of samples falling in the HbA₂ "borderline" and "normal" categories, it can be concluded that HbA₂ has a measure of unreliability in the diagnosis of β-thalassemia carriers.

Capillarys 2 Flex Piercing: Analytical performance assessment according to CLSI protocols for HbA1c quantification

HbA_1c is used for monitoring diabetic balance. In this paper we report an assessment of the analytical performances of Capillarys 2 Flex Piercing (C2FP) for HbA_1c measurement using CE (Capillary Electrophoresis). CLSI (Clinical and Laboratory Standard Institute) protocols are used for the evaluation of apparatus performances: precision, linearity, method comparison, trueness and common interferences. HbA_1c CVs average in intra-assay was 1.6% between run imprecision CV ranged from 0.1 to 1.8%. The linearity was demonstrated between 4.7 and 15.0%. The comparison study revealed that Bland Altman plot mean difference was equal to -0.03 (CI 95% (-0.05 to -0.0003)) and Passing-Bablok regression intercept was -0.05, CI95%(-0.13 -  -0.05); slope: 1.00, CI95%[1.00-1.01]. A strong correlation (r > 0.99) was proved. No significant effects of hemoglobin variants were seen with CE on HbA_1c measurement. No problem related to sample-to-sample carry over was noted. No interferences of LA_1c and cHb were observed. CE allowed quantification of HbA_1c even at low level of total hemoglobin (40 g/L) in contrast to HPLC. Furthermore, this analyzer offered the opportunity of quantifying the HbA₂ simultaneously with HbA_1c . This evaluation showed that C2FP is a convenient system for the control of diabetes and the detection of hemoglobinopathies.

Hemoglobin Analysis in the First Year of Life

BACKGROUND AND OBJECTIVES

In newborns and infants during their first year of life, there is a dynamic change in the fraction of hemoglobin (Hb). To apply Hb analysis as a phenotypic diagnosis of thalassemia in newborns and infants, we need normal values of each Hb fraction for reference.

METHODS

Seventeen cord bloods from normal deliveries were collected for analysis. One hundred and thirty-seven infants from the pediatric outpatient clinic were recruited and were categorized by their ages into a series of short periods (month±2 weeks). Both alpha and beta thalassemia carriers detected were excluded. Samples with an Hb level less than 10.0 g/dL were also excluded. The proportion of Hb A (α2β2), A2 (α2δ2), and F (α2γ2) was obtained from high-performance liquid chromatography and analyzed according to its categorized periods.

RESULTS

There were 90 (58.4%) specimens left for evaluation. The percentage of Hb A, A2, and F gradually changed with increasing age. The percentage of Hb A was 21.14±7.04% (mean±SD) in cord blood and increased substantially to 83.38±1.31% at the sixth month. The level was sustained thereafter. The incremental pattern of Hb A2 was similar to Hb A. The value was 0.32±0.19% at the beginning and reached a plateau with 2.78±0.25% at the sixth month. The percentage of Hb F started at 78.39±7.59% in cord blood and decreased rapidly in the first 6 months.

CONCLUSIONS

The data possibly can be applied as quick guidance for interpretation of Hb analysis in newborns and infants during their first year of life.

Hemoglobin A2 values in sickle cell disease patients quantified by high performance liquid chromatography and the influence of alpha thalassemia

Background

In sickle cell disease, the quantification of Hb A₂ is important for the differential diagnosis between sickle cell anemia (Hb SS) and Hb S/β⁰-thalassemia.

Objective

To determine Hb A₂ levels as quantified by high performance liquid chromatography in patients with sickle cell anemia (Hb SS) and with the SC hemoglobinopathy, with or without concomitant alpha thalassemia.

Methods

This is a retrospective study of 242 children aged between two and six years with diagnoses of Hb SS or Hb SC. The hemoglobin was evaluated using high performance liquid chromatography and alpha thalassemia [3.7 kb deletion (−α^3.7)] was detected by polymerase chain reaction. Patients were classified as homozygous (−α^3.7/−α^3.7), heterozygous (−α^3.7/α), or homozygous wild-type. Analysis of variance was used to compare the mean Hb A₂ values between the alpha thalassemia groups.

Results

The mean (± standard deviation) Hb A₂ concentrations in the Hb SS group (n = 135) was 3.68 ± 0.65%. The mean values for individuals with Hb SS and heterozygous (n = 28) or homozygous for alpha thalassemia (n = 3) were 3.98 ± 0.64% and 4.73 ± 0.25%, respectively. The mean Hb A₂ of all the Hb SC patients (n = 107) was 4.01 ± 0.507 with 4.29 ± 0.41% and 4.91 ± 0.22% in individuals heterozygous (n = 23) and homozygous for alpha thalassemia (n = 7), respectively. All patients homozygous for alpha thalassemia had Hb A₂ levels above 3.5%. However, Hb A₂ values above 5.2% were seen in patients with Hb SS and Hb SC, independently of alpha thalassemia.

Conclusion

Hb A₂ levels are elevated in patients with Hb S or Hb C, and are directly influenced by the alpha thalassemia genotypes.

Detection of compound heterozygous of hb constant spring and hb q-Thailand by capillary electrophoresis and high performance liquid chromatography

A capillary electrophoresis (CE) has proven to be superior to a high performance liquid chromatography (HPLC) in the detection of hemoglobin Constant Spring (Hb CS). Thus the aim of this study was to analyze the efficacy of CE and HPLC for the detection of Hb CS in samples with compound heterozygous of Hb CS and Hb Q-Thailand. Hemoglobin analysis was performed in blood samples of 2 patients with compound heterozygous of Hb CS and Hb Q-Thailand by using HPLC and CE. The HPLC chromatogram and CE electrophoregram of the two techniques were compared. Hb CS was not found on HPLC chromatogram while Hb QA2 (α2 (QT)δ2), a derivative of Hb Q-Thailand, was presented at the retention time of 4.70-4.80 min and it was close to the retention time of Hb CS. On CE electrophoregram, Hb CS was presented at zone 2 (Z2) and it was distinctly separated from Hb QA2 which was presented at Z1. Therefore, CE was more efficient to the HPLC for diagnosis of compound heterozygous of Hb CS and Hb Q-Thailand.

Comparative analysis of cellulose acetate hemoglobin electrophoresis and high performance liquid chromatography for quantitative determination of hemoglobin A2

Background

The present study is designed to evaluate the reliability and cost effectiveness of cellulose acetate Hb electrophoresis and high performance liquid chromatography (HPLC) in the determination of HbA2 levels.

Methods

The test population comprised 160 individuals divided into four groups: normal individuals, β-thalassemia trait (BTT) patients, iron deficiency anemia (IDA) patients, and co-morbid patients (BTT with IDA). HbA2 levels determined using cellulose acetate Hb electrophoresis and HPLC were compared.

Results

HbA2 levels were found to be diagnostic for classical BTT using either method. In co-morbid cases, both techniques failed to diagnose all cases of BTT. The sensitivity, specificity, and Youden's index for detection of the co-morbid condition was 69% and 66% for HPLC and cellulose acetate Hb electrophoresis, respectively.

Conclusion

This study revealed that semi-automated cellulose acetate Hb electrophoresis is more suitable for use in β-thalassemia prevention programs in low-income countries like Pakistan. This technique is easily available, simple and cost effective.

Detection of Abnormal Hemoglobin Variants by HPLC Method: Common Problems with Suggested Solutions

Thalassemia and thalassemic hemoglobinopathies pose serious health problem leading to severe morbidity and mortality in Indian population. Plethora of hemoglobin variants is prevalent in multiethnic Indian population. The aim of the present study was to analyze laboratory aspects, namely, hematological profile and HPLC findings of the hemoglobin variants detected, and to discuss problems that we faced in diagnosis in a routine clinical laboratory. We screened a total of 4800 cases in a hospital based population of North India in a 2-years period of by automated HPLC method using the Variant Hemoglobin Testing System (Variant II Beta Thalassemia Short Program, Bio-Rad Laboratories) under the experimental conditions specified by the manufacturer. Whole blood in EDTA was used and red cell indices were determined using automated hematology analyzer. We detected 290 cases with abnormal variants in which beta thalassemia was the most common followed by hemoglobin E. Here, we discuss the laboratory aspects of various hemoglobin disorders and diagnostic difficulties in cases like borderline HbA2 values, presence of silent mutation, alpha thalassemia gene, and few rare variants which at times require correlation with genetic study. Special attention was given to HbA2 level even in presence of a structural variant to rule out coinheritance of beta thalassemia gene.

Automated capillary electrophoresis in the screening for hemoglobinopathies

Hemoglobinopathies are genetic disorders of globin chains characterized by the decreased expression of α- or β-globin chains (thalassemias) or by the synthesis of an abnormal protein (hemoglobin variants in, e.g., sickle cell disease). The screening of most hemoglobinopathies relies, together with hematological results and clinical elements, on the separation and quantification of normal and abnormal hemoglobin fractions. Gel electrophoresis, isoelectric focusing, and HPLC have been the methods of choice for many years. For about 20 years, capillary electrophoresis has appeared as a strong alternative method. Since the early 2000s, automated instruments are commercially available for the analysis of Hb fractions in adult patients but also for neonatal screening.

Capillary zone electrophoresis for haemoglobinopathy diagnosis

Aims

Capillary zone electrophoresis (CE) at alkaline pH is increasingly used in haemoglobinopathy diagnosis. We report our evaluation of automated CE, using the Capillarys 2 Flex Piercing instrument, as a routine diagnostic method for the detection of variant haemoglobins and the diagnosis of β thalassaemia.

Methods

A Capillarys 2 Flex Piercing instrument with Phoresis software was evaluated in our laboratory over a 6-week period, comparisons being made with high performance liquid chromatography (HPLC) and, for haemoglobin A2 quantification, with microcolumn chromatography.

Results

The instrument was easy to use and was suitable for the quantification of haemoglobin A2. Quantification of A2 was precise and the percentage was stable with ageing of the blood specimen. Results differ among HPLC, CE and microcolumn chromatography and use of an instrument-specific, method-specific reference range is therefore recommended until such time as there is standardisation between methods and manufacturers. Common variant haemoglobins were provisionally identified without difficulty. There are some uncommon variant haemoglobins that are detected by HPLC but not by capillary electrophoresis, but the reverse also occurs.

Conclusions

Capillary electrophoresis using a Capillarys 2 Flex Piercing instrument is suitable for haemoglobinopathy diagnosis.

Association of Hb New York with Hb E and α(0)-thalassemia in a Chinese woman identified by Sebia CapillaryS2 system

We describe a Chinese woman who was assumed to be heterozygous for both Hb E [β26(B8)Glu→Lys] and α(0)-thalassemia (α(0)-thal) by a high performance liquid chromatography (HPLC) method, but was later also shown to be a Hb New York [β113(G15)Val→Glu] heterozygote by the Sebia CapillaryS2 system. This study suggested that a single test is never sufficient to allow the correct diagnosis of an abnormal hemoglobin (Hb). We also emphasize the importance of a correct diagnosis of interactions between α- and β-thalassemias.

Interlaboratory comparison of current high-performance methods for HbA2

INTRODUCTION

Few data are available on the alignment of the different methods used for HbA(2) quantitation and recent external quality survey results show a consistent spread of HbA(2) values. To this aim, a comparison study among the actual best performing techniques for HbA(2) determination, comprising HPLC and CE methods, was performed.

METHODS

A total of 80 blood samples collected from normal subjects and β-thalassemia carriers were analyzed by different HPLC (Bio-Rad Variant I, Bio-Rad Variant II, Menarini HA-8160, Tosoh G7, Tosoh G8) and capillary electrophoresis (Beckman Coulter MDQ and ProteomeLab PA 800, Sebia Capillarys 2) methods. Patient's samples with clinically relevant hemoglobin variants (HbC, HbD, HbE, HbS, and δ-chain variants) were also tested by all methods.

RESULTS

The mean within-run imprecision of HbA(2) measurement (expressed as CV, %) was between 0.5% and 4.4% (HPLC) and between 1.2% and 4.4% (capillary electrophoresis). The comparison study showed that the different methods were highly correlated (r between 0.974 and 0.997) although biased each other. HbA(2) determination in presence of abnormal hemoglobins was variously interfered by both HPLC and CE methods. Concerning HbF, the mean imprecision at HbF values ≥1.5% was between 1.2% and 8.2% (as CVs).

CONCLUSIONS

A poor alignment of routine methods for HbA(2) measurement was found. The need of a better standardization of HbA(2) measurement procedures was underlined.

Comparison of capillary electrophoresis with cellulose acetate electrophoresis for the screening of hemoglobinopathies

BACKGROUND

β-thalassemia is primarily found in individuals of Mediterranean and Southeast Asian ancestry. With rapid growth in the Southeast Asian segments of the Korean population, the geographic distribution of hemoglobinopathies is expected to become significantly different from what it is today. In this study, Hb fractions were measured in patients with hypochromic microcytosis to detect thalassemia and Hb variants. To evaluate the feasibility of replacing cellulose acetate electrophoresis (CA) with capillary electrophoresis (CE) in a clinical laboratory, both techniques were performed and the outcomes were compared.

METHODS

To evaluate hemoglobinopathies, complete blood cell counts (CBC), CA, and CE were carried out on samples from healthy and microcytic hypochromic groups. The microcytic hypochromic group consisted of 103 patients whose mean corpuscular volume (MCV) was less than 75 fL and mean corpuscular hemoglobin (MCH) was less than 24 pg. Quantitative analysis of Hb fractions was performed on 143 whole blood samples.

RESULTS

There was a good correlation for measurements of HbA (r=0.9370, P<0.0001), HbA(2) (r=0.8973 P<0.0001), and HbF (r= 0.8010, P=0.0304) between the two methods. In the microcytic hypochromic group, there were 29 cases (28.2%) with decreased HbA(2), 2 cases (1.9%) with increased HbA(2), 3 cases (2.9%) with increased HbF, and 2 cases (1.9%) with increased HbA(2) and HbF.

CONCLUSIONS

CE is comparable to CA for reliable measurement of Hb fractions. It is suitable for screening of hemoglobinopathies in many clinical laboratories.

Interference of hemoglobin Hope on beta-thalassemia diagnosis by the capillary electrophoresis Method

The β-chain hemoglobin (Hb) variants interfere with the diagnosis of β-thalassemia trait using high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE). We analyzed the effect of Hb Hope, a β-chain Hb variant frequently found in the Thai population, on β-thalassemia trait diagnosis. HPLC and CE were used to quantify the level of HbA(2) in 11 whole blood samples containing Hb Hope. The levels of Hb Hope detected by both methods were similar. An elevated HbA(2) level was found in all samples analyzed by the CE method, while 1 was increased when analyzed by HPLC, which was a compound heterozygous of Hb Hope and α-thalassemia-1 SEA-type deletion. Of 11 samples, 6 had mean corpuscular volumes within the reference range. All samples showed negative results for molecular analysis of β(0)-thalassemia codon 17, 41/42, and 71/72 mutations and β-thalassemia 3.5-kb deletion. Therefore, Hb Hope interfered with the diagnosis of β-thalassemia trait analyzed by CE but not by HPLC.