SUPT5H mutations associated with elevation of Hb A2 level: Identification of two novel variants and literature review

β-thalassemia is one of the most common monogenic disorders in areas of the tropics and subtropics, which represents a major familial and social burden to local people. The elevated Hb A2 level, generally specified as greater than 3.5 %, is commonly used as a high efficiency index for screening of β-thalassemia carriers. However, mutations in other genes such as GATA1 and KLF1, could also result in increased Hb A2 level. In this study, we identified two novel variants in the SUPT5H gene: a frameshift mutation (SUPT5H: c.3032_3033delTG, p.M1011Mfs*9) and a nonsense mutation (SUPT5H: c.397C > T, p.Arg133*) in two Chinese individuals. Utilizing a combination of phenotype analysis, bioinformatics analysis, and functional analysis, we deduced that these two variants modified the SUPT5H protein's structure, thereby impacting its function and consequently leading to the heightened Hb A2 level phenotype found in the carriers. Furthermore, through a comprehensive literature review, a mutation spectrum was consolidated for SUPT5H, an investigation into the genotype-phenotype correlation was conducted, and factors known to influence Hb A2 levels were identified. Based on this in-depth understanding, clinicians are better equipped to carry out large scale screenings in regions with high prevalence of β-thalassemia.

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.

Label-free quantification of host cell protein impurity in recombinant hemoglobin materials

Quantitative analysis relies on pure-substance primary calibrators with known mass fractions of impurity. Here, label-free quantification (LFQ) is being evaluated as a readily available, reliable method for determining the mass fraction of host cell proteins (HCPs) in bioengineered proteins which are intended for use as protein calibration standards. In this study a purified hemoglobin-A2 (HbA2) protein, obtained through its overexpression in E. coli, was used. Two different materials were produced: natural and U15N-labeled HbA2. For the quantification of impurities, precursor ion (MS1-) intensities were integrated over all E. coli proteins identified and divided by the intensities obtained for HbA2. This ratio was calibrated against the corresponding results for an E. coli cell lysate, which had been spiked at known mass ratios to pure HbA2. To demonstrate the universal applicability of LFQ, further proteomes (yeast and human K562) were then alternatively used for calibration and found to produce comparable results. Valid results were also obtained when the complexity of the calibrator was reduced to a mix of just nine proteins, and a minimum of five proteins was estimated to be sufficient to keep the sampling error below 15%. For the studied materials, HbA2 mass fractions (or purities) of 923 and 928 mg(HbA2)/g(total protein) were found with expanded uncertainties (U) of 2.8 and 1.3%, resp. Value assignment by LFQ thus contributes up to about 3% of the overall uncertainty of HbA2 quantification when these materials are used as calibrators. Further purification of the natural HbA2 yielded a mass fraction of 999.1 mg/g, with a negligible uncertainty (U = 0.02%), though at a significant loss of material. If an overall uncertainty of 5% is acceptable for protein quantification, working with the original materials would therefore definitely be viable, circumventing the need of further purification.

Molecular Characterization of Haemoglobin E

OBJECTIVE

To detect mutation in cases having haemoglobin A2 level >7% on high performance liquid chromatography.

METHODS

The cross-sectional, descriptive study was conducted from July 2017 to December 2018 at the Department of Haematology and Human Genetics and Molecular Biology, University of Health Sciences, Lahore, Pakistan, and comprised patients of either gender with haemoglobin A2 ≥7%. The samples were collected from different cities of Punjab in collaboration with the Punjab Thalassemia Prevention Programme, Lahore. The samples were subjected to complete blood count and high performance liquid chromatography using automated haematology analysers and variant-II beta thalassemia short programme, respectively. To analyse haemoglobin E mutations at the molecular level, polymerase chain reaction-restriction fragment length polymorphism (PCR_RFLP) was performed using a type IIS restriction endonuclease known as Mnl1 (derived from Moraxella nonliquefaciens) to cleave DNA at specific sites and the results were further confirmed on randomly selected samples using Sanger sequencing. Data was analysed using SPSS 25.

RESULTS

Of the 39 patients, 15(38.5%) were males and 24(61.5%) were females. The overall median age was 14 (23) years. There were 29 (74.4%) patients with thalassemia family history, and 22(56.4%) had a positive family history of transfusion related to thalassemia, while no patient had a family history of iron therapy. The median haemoglobin A, haemoglobin A2 and haemoglobin F levels were 72.2 (65.2-79.1) %, 26.6 (19.1-34.0) % and 0.9 (-0.8-2.6) %, respectively. After molecular investigation, HbAE mutation was found in 23(59%) patients, while wild type HbAA genotype was found in 16(41%). The heterozygous HbE mutation was present in 23(59%) patients.

CONCLUSIONS

Frequently missed/undiagnosed cases of haemoglobin E that co-elute with haemoglobin A2 in the same high performance liquid chromatography window were detected among those with haemoglobin A2 ≥7%.

Factors affecting the evaluation and use of a hemoglobin A2 method – lot-to-lot variation, long-term deviation and carry-over

BACKGROUND

We compared two Hb A₂ methods, high pressure liquid chromatography and capillary zone electrophoresis, at two occasions. In 2014 the methods showed good agreement, while in 2020 HPLC results were clearly higher than CE results. This finding prompted us to investigate the external quality assessment (EQA) outcome and our total patient results obtained by high pressure liquid chromatography over several years.

METHODS

The methods compared were Bio-Rad Variant II Beta-Thal Short Program (HPLC) and Sebia Capilllarys Flex Piercing (CE).

RESULTS

Our annual patient results obtained by HPLC increased significantly from 2014 to 2020. A similar trend was also seen in our EQA results. When patient results were grouped according to different reagent lots it became evident that method comparisons might be severely affected by lot-to-lot variation. We also noticed that samples analyzed with the HPLC method following a sample containing a high proportion of Hb E where prone to give falsely increased Hb A₂ results.

CONCLUSION

Standardization of the measurement of Hb A₂ is urgently needed. Furthermore, the lot-to-lot variation must be minimized. While waiting for these improvements each laboratory ought to repeatedly evaluate their distribution of patient Hb A₂ results.

Establishment of pregnant-specific intervals for hemoglobin (Hb) A2, HbF and cut-off points for HbA2 for thalassemia in Chongqing, China

OBJECTIVES

To analyze pregnant-specific intervals for hemoglobin A2 (HbA2), hemoglobin fetal (HbF), and cut-off points of HbA2 for thalassemia in Chongqing, China.

METHODS

Between September 2015 and April 2019, the study recruited 10039 individuals of reproductive age. Of which, 4399 healthy normal individuals were selected to determine reference values for HbA2 and HbF. The remaining 5640 individuals suspected of thalassemia were included to explore the cut-off points of HbA2 for thalassemia.

RESULTS

The reference values of HbA2 in males was 2.3-3.2%, in females was 2.1-3.1%, and in pregnant women was 1.9-3.1%. While the reference values of HbF in males was 0.0-0.0%, in females was 0.0-0.9%, and in pregnant women was 0.0-4.3%. Approximately 2.3% cut-off points for pregnant women was determined to be optimal for α-thalassemia screening. In the entire group, 2.5% was best for all α-thalassemia screenings. The cut-off for β-thalassemia screening using HbA2 was 3.2% for the entire group.

CONCLUSION

The reference interval of HbA2 for pregnant females group was significantly lower than other groups. Therefore, we recommend cut-off points of HbA2 for α-thalassemia at 2.3% for pregnant women. While partitioning was not needed due to gender. Gender and pregnancy had little effect on the cut-off points of HbA2 for β-thalassemia carrier.

[Genetic Analysis of Thalassemia in 22 940 Pregnant Women in Xiangxi Tujia and Miao Autonomous Prefecture]

OBJECTIVE

To investigate the incidence and types of thalassemia in Xiangxi Tujia and Miao Autonomous Prefecture.

METHODS

Automatic capillary electrophoresis was used to screen the thalassemia phenotypes of 22 940 blood samples of pregnant women and puerperants collected in our hospital and some other medical institutions in the prefecture during 2017-2019, among which there were 3 356 cases of Tujia ethnicity, 2 821 cases of Miao ethnicity, and 2 233 cases of Han ethnicity included, whose ethnicity were indicated. The samples with positive result would undergo further genetic testing.

RESULTS

There were 2 314 cases of suspicious thalassemia were screened from 22 940 cases by the electrophoresis, thus the positive rate was 10.1% (hematological phenotypes from some other institutions were not included). Specifically, there were 1 706 cases with HBA₂ less than 2.5%, 255 cases with HBA₂ ranged from 2.5% to 3.5%, which displayed abnormal hematology (MCV or/and MCH) or other abnormal bands, and 353 cases with HBA₂>3.5%. There were 436 suspected positive patients in 2 314 suspicious samples received further thalassemia gene testing in our hospital, among them 48 cases were diagnosed with α-thalassemia, 85 cases with β-thalassemia, and 2 cases as compound type. The positive diagnosis rate of α-thalassemia gene test was 11.0%, β-thalassemia was 19.4%, and positive pregnant women was 31.0%.

CONCLUSION

The positive rate of thalassemia screening in Xiangxi Autonomous Prefecture is roughly the same as that in other regions of Hunan. The positive predictive value of β-thalassemia screening is as high as 86%. Compared with the missed screening data, it is recommended to use hematology (MCV, MCH) method combined with capillary hemoglobin electrophoresis for thalassemia screening.

Importance of Sequencing HBA1, HBA2 and HBB Genes to Confirm the Diagnosis of High Oxygen Affinity Hemoglobin

High oxygen affinity hemoglobin (HOAH) is the main cause of constitutional erythrocytosis. Mutations in the genes coding the alpha and beta globin chains (HBA1, HBA2 and HBB) strengthen the binding of oxygen to hemoglobin (Hb), bringing about tissue hypoxia and a secondary erythrocytosis. The diagnosis of HOAH is based upon the identification of a mutation in HBA1, HBA2 or HBB in specialized laboratories. Phenotypic studies of Hb are also useful, but electrophoretic analysis can be normal in 1/3 of cases. The establishment of the dissociation curve of Hb can be used as another screening test, a shift to the left indicating an increased affinity for Hb. The direct measurement of venous P50 using a Hemox Analyzer is of great importance, but due to specific analytic conditions, it is only available in a few specialized laboratories. Alternatively, an estimated measurement of the P50 can be obtained in most of the blood gas analyzers on venous blood. The aim of our study was therefore to determine whether a normal venous P50 value could rule out HOAH. We sequenced the HBB, HBA1 and HBA2 genes of 75 patients with idiopathic erythrocytosis. Patients had previously undergone an exhaustive medical check-up after which the venous P50 value was defined as normal. Surprisingly, sequencing detected HOAH in three patients (Hb Olympia in two patients, and Hb St Nazaire in another). A careful retrospective examination of their medical files revealed that (i) one of the P50 samples was arterial; (ii) there was some air in another sample; and (iii) the P50 measurement was not actually done in one of the patients. Our study shows that in real life conditions, due to pre-analytical contingencies, a venous P50 value that is classified as being normal may not be sufficient to rule out a diagnosis of HOAH. Therefore, we recommend the systematic sequencing of the HBB, HBA1 and HBA2 genes in the exploration of idiopathic erythrocytosis.

[The value of combined detection of HbA2 and HbF for the screening of thalassemia among individuals of childbearing ages]

OBJECTIVE

To assess the application value of combined detection of HbA2 and HbF for the screening of thalassemia among a population of childbearing age in Quanzhou, Fujian, and determine the optimal cut-off values for the region.

METHODS

Capillary hemoglobin electrophoresis and genetic testing for α and β globin gene mutations were simultaneously carried out on 11 428 patients with suspected thalassemia. Statistical methods were used to analyze the distribution of various types of thalassemia and compare the performance of HbA2 and HbF measurement for the screening of various types of thalassemia. The optimal cut-off values for HbA2 and HbF were determined with the ROC curves.

RESULTS

4591 patients with α, β, and αβ compound thalassemia were identified by genetic testing. The most common genotypes for α and β thalassemia included --SEA/αα and β654/βN, β41-42/βN, and β17/βN. The ROC curves were drawn to compare the performance of HbA2 screening for α-, β-, αβ-compound, static α-, mild α-, and intermediate α-thalassemia, and the maximum area under the curves was 0.674, 0.984, 0.936, 0.499, 0.731, 0.956, and the optimal cut-off values for HbA2 were 2.45%, 3.25%, 3.65%, 2.95%, 2.55%, 1.75%, respectively.

CONCLUSION

HbA2 is an efficient indicator for identifying intermediate types of α-, β-, and αβ compound thalassemia. The combination of HbA2 and HbF measurement can effectively detect carriers for β-thalassemia mutations.

A roadmap for the standardization of hemoglobin A2

BACKGROUND

Standardization of laboratory tests can be a long process, and this is the case with regards to the methods used to measure hemoglobin A₂ (HbA₂), an important marker for beta-thalassemia and other thalassemic conditions. The IFCC standardization project started in 2004, and it took at least 15 years before developing a reference measurement procedure, defining and producing calibrators and certified reference materials.

METHODS

A series of steps have to be undertaken in order to promote the standardization in the field, a process involving a number of stakeholders (manufacturers, scientific societies, national health bodies, laboratory professionals, clinicians). In this work we describe some possible process indicators, in order to assure that the standardization will have internal and external validity and be effective for a long time. These indicators concern the inter-method studies, elaboration of External Quality Assessment Schemes, and the evaluation of the yearly distributions of HbA₂ measurements collected in selected laboratories.

RESULTS

Preliminary results are reported concerning the yearly distributions of HbA₂, collected in two different locations, and using different analytical methods. Median yearly values were found very constant over the years, but different between methods. On the other side, results obtained on the same specimens using two different techniques, proved that results by capillary electrophoresis in 2 out of the 3 years of observation, were significantly lower than those by HPLC.

CONCLUSION

In this document we report what has been done so far, and what has to be done to achieve the standardization of the measurement of HbA₂ worldwide.

Correlation Of Serum Ferritin With Haemoglobin A2 Level In Beta Thalassemia Traits

BACKGROUND

Haemoglobin-A2 is considered as a paramount diagnostic parameter for the detection of beta-thalassemia trait which may vary with the fluctuation of body iron stores. The current study aims to evaluate the correlation of serum ferritin as a parameter of body iron stores with haemoglobin-A2 level in beta-thalassemia traits.

METHODS

This cross-sectional study was conducted on total 134 known beta-thalassemia traits in Rehman Medical Institute-Peshawar, Pakistan from October 2018 to June 2019. Blood samples from the contributors were drawn in EDTA and plain tubes for complete blood counts, haemoglobin-A2 and serum ferritin estimation. Participants were categorized into 3 groups on the basis of iron status; beta-thalassemia traits with low ferritin (Group A), normal ferritin (Group B) and high ferritin levels (Group C). Pearson correlation was applied to analyse the correlation between the variables.

RESULTS

Out of total 134 known beta-thalassemia traits, 73 (54.5 %) were males and 61 (45.5%) were females. Participants of group A with low ferritin were 22 (16.4%), group B with normal ferritin were 96 (71.6%) and group C with high ferritin were 16 (11.9%). Group A shows lowest mean haemoglobin-A2 level comparatively to Group B and Group C, with some effect of serum ferritin on haemoglobin-A2 level.

CONCLUSIONS

Haemoglobin-A2 value decreases when there is a decrease in serum ferritin and show slightly increase with high ferritin level as compared to normal ferritin level or body iron stores in beta-thalassemia traits. However, this correlation is not significant enough to mask the actual diagnosis of the disease.

Capillary Electrophoresis Resolves Inconclusive HPLC Analysis for Hemoglobin Variants: a Study of Two Cases

BACKGROUND

Hb I and Hb Shaare Zedek are rare hemoglobin variants in the Chinese population. High-performance liquid chromatography (HPLC) is a widely used technique for screening of thalassemias and hemoglobin variants in Chinese primary hospitals. However, some rare hemoglobin variants cannot be effectively separated by HPLC. Here, we report one case of Hb I and one case of Hb Shaare Zedek which could not be detected by HPLC but required capillary electrophoresis (CE) in our hospital.

METHODS

Two blood samples with high Hb F level were analyzed by HPLC as part of routine screening, and then globin genes were analyzed using Gap-PCR, PCR-Reverse dot-blot (RDB), and DNA sequencing. Subsequently, samples were analyzed by CE and results compared to HPLC.

RESULTS

In case 1, results were as follows: Hb F 16.9%, Hb A0 72.5% (failed to show the value of Hb A in HPLC) and Hb A2 2.2% for HPLC. No mutations were detected using Gap-PCR and PCR-RDB, but there was a mutation of codon (CD) 16 in the α2 globin gene (AAG>GAG, corresponds to Hb I) by DNA sequencing. CE showed Hb A2 1.9%, Hb A 74%, Hb I 24.1%. In case 2, results were as follows: Hb F 11.0%, Hb A0 76.6%, and Hb A2 4.7% for HPLC. It showed a CD 41 - 42 mutation of the β-globin gene (-TTCT) using PCR-RDB and the CD 56 mutation in α2/α1 globin gene (AAG>GAG, corresponding to Hb Shaare Zedek) with DNA sequencing. CE displayed Hb A2 4.5%, Hb A 84.6%, Hb F 0.4%, Hb Shaare Zedek 10.5%.

CONCLUSIONS

Hb I and Hb Shaare Zedek cannot be separated by HPLC because of co-elution with Hb F. However, they were identified and quantified using CE. As a general precaution, therefore, and owing to the existence of rare variants that may co-elute with normal hemoglobin fractions, it is recommended to use at least two complementary methods for the diagnostic detection of hemoglobin species.

A rapid quantification method for the screening indicator for β-thalassemia with near-infrared spectroscopy

Near-infrared (NIR) spectroscopy combined with chemometrics was applied to rapidly analyse haemoglobin A2 (HbA₂) for β-thalassemia screening in human haemolysate samples. The relative content indicator HbA₂ was indirectly quantified by simultaneous analysis of two absolute content indicators (Hb and Hb∙HbA₂). According to the comprehensive prediction effect of the multiple partitioning of calibration and prediction sets, the parameters were optimized to achieve modelling stability, and the preferred models were validated using the samples not involved in modelling. Savitzky-Golay smoothing was firstly used for the spectral pretreatment. The absorbance optimization partial least squares (AO-PLS) was used to eliminate high-absorption wave-bands appropriately. The equidistant combination PLS (EC-PLS) was further used to optimize wavelength models. The selected optimal models were I=856nm, N=16, G=1 and F=6 for Hb and I=988nm, N=12, G=2 and F=5 for Hb∙HbA₂. Through independent validation, the root-mean-square errors and correlation coefficients for prediction (RMSEP, R_P) were 3.50gL^-1 and 0.977 for Hb and 0.38gL^-1 and 0.917 for Hb∙HbA₂, respectively. The predicted values of relative percentage HbA₂ were further calculated, and the calculated RMSEP and R_P were 0.31% and 0.965, respectively. The sensitivity and specificity for β-thalassemia both reached 100%. Therefore, the prediction of HbA₂ achieved high accuracy for distinguishing β-thalassemia. The local optimal models for single parameter and the optimal equivalent model sets were proposed, providing more models to match possible constraints in practical applications. The NIR analysis method for the screening indicator of β-thalassemia was successfully established. The proposed method was rapid, simple and promising for thalassemia screening in a large population.

Coinheritance of B-Thalassemia and Sickle Cell Anaemia in Southwestern Nigeria

BACKGROUND

Genes for haemoglobin S are found in high frequencies in Nigeria. However, there is little information on beta thalassemia in sickle cell anaemia in this population. The clinical presentation of HbS- β thalassemia is enormously variable, ranging from an asymptomatic state to a severe disorder similar to homozygous sickle cell disease.

MATERIALS AND METHODS

Haemoglobin A2 and HbF were determined in sickle cell anaemia patients attending LAUTECH Teaching Hospital, Osogbo, by elution after electrophoresis and alkaline denaturation methods respectively. Haematological parameters were estimated using Sysmex KX-21N and percentage target cells using Leishman's staining technique.

RESULTS

Exactly 6% f the SCA patients were found to have elevated HbA2 (>3.3%) and HbF (>1.3%). These patients also had normal erythrocyte indices, increased platelet count, a significantly higher HCT and an increased % target cell.

CONCLUSION

These findings confirm that the frequency of beta thalassaemia in sickle cell patients in Nigeria is higher than previously thought. It is therefore important to consider the possibility of this variant in patients with sickle cell anaemia since their course may differ from that of patients with homozygous sickle cell anaemia.

Evaluation of the V8 E-Class, a Novel Automated Capillary Isoelectric Focusing Instrument for Hemoglobinopathy Screening

OBJECTIVES

We evaluated the performance of a novel capillary isoelectric focusing (CIEF) application for hemoglobinopathy screening on the recently introduced V8 E-Class platform.

METHODS

Analytical performance of the V8 E-Class was evaluated and included assessment of hemoglobin A2 (HbA2) imprecision; linearity for HbA2, fetal hemoglobin (HbF), and sickle hemoglobin (HbS); and carryover for HbS. Furthermore, a method comparison with the Minicap Flex Piercing (Sebia, Lisses, France), the Variant Classic (Bio-Rad Laboratories, Hercules, CA), and the G8 (Tosoh Europe, Amsterdam, the Netherlands) was done to assess analytical and clinical concordance.

RESULTS

Total HbA2 imprecision was 3.26% and 3.14% for normal and elevated HbA2 controls and 5.16% and 3.58% for a normal and a heterozygous HbS patient sample, respectively. HbA2, HbF, and HbS showed acceptable linearity, and no carryover was observed. The method comparison showed good analytical concordance (r > 0.95) except for a homozygous HbS subset (r = 0.532-0.704). A comparable phenomenon was seen for the clinical concordance with good agreement in samples without variants (weighted κ > 0.80) but poorer agreement in HbS samples (κ < 0.30).

CONCLUSIONS

Good analytical performance was demonstrated for this novel CIEF application for hemoglobinopathy screening. Method comparison showed generally good correlation but highlights the need for standardization. Finally, software optimization could further add to its use for routine hemoglobinopathy screening.

Prevalence of thalassaemia, iron-deficiency anaemia and glucose-6-phosphate dehydrogenase deficiency among Arab migrating nomad children, southern Islamic Republic of Iran

This study investigated the prevalence of iron-deficiency anaemia, glucose-6-phosphate dehydrogenase (G6PD) deficiency and β-thalassaemia trait among Arab migrating nomad children in southern Islamic Republic of Iran. Blood samples were analysed from 134 schoolchildren aged < 18 years (51 males, 83 females). Low serum ferritin (< 12 ng/dL) was present in 17.9% of children (21.7% in females and 11.8% in males). Low haemoglobin (Hb) correlated significantly with a low serum ferritin. Only 1 child had G6PD deficiency. A total of 9.7% of children had HbA2 ≥ 3.5 g/dL, indicating β-thalassaemia trait (10.8% in females and 7.8% in males). Mean serum iron, serum ferritin and total iron binding capacity were similar in males and females. Serum ferritin index was as accurate as Hb index in the diagnosis of iron-deficiency anaemia. A high prevalence of β-thalassaemia trait was the major potential risk factor in this population.

Higher sensitivity of capillary electrophoresis in detecting hemoglobin A2'compared to traditional gel electrophoresis

HbA2' (also called Hb B2) is the most common delta-globin chain defect and is reported to occur in 1-2% of the African American population. The major clinical significance of HbA2' is that the failure to detect it might lead to an underestimation of the total HbA2, leading to failure to diagnose β-thalassemia minor. In order to diagnose β-thalassemia minor, both HbA2 and HbA2' levels must be combined.Hb A2' accounts for a small percentage (1-2%) of the total hemoglobin in heterozygotes. It is difficult to detect this small amount by traditional gel electrophoresis. Using HPLC Hb A2' is easily detected as it produces a minor peak in the S window. Other conditions which might interfere with detection of HbA2' by HPLC include Hb S trait or Hb SS disease (Hb A2' hidden in the S peak), transfused Hb SS (Hb S peak may be very small), Hb C trait or Hb CC disease (glycosylated Hb C elutes in the S window), and Hb G (Hb G2 elutes in the S window). All of the above conditions, including Hb A2', occur most commonly in the same ethnic group (African American). We reviewed 654 consecutive cases over a period of three months for the presence of Hb A2' in our laboratory where capillary electrophoresis is used as the primary diagnostic tool. We detected seven cases (1.07 %) of HbA2'. In contrast, we did not detect any HbA2' using conventional gel electrophoresis in the last one year (2,580 cases). Although in none of the seven cases the sum of Hb A2 and Hb A2' exceeded 3.5%, we believe that capillary electrophoresis allows for a better detection of Hb A2' than gel electrophoresis and HPLC.

Screening immediate family members for carrier identification and counseling: a cost-effective and practical approach

OBJECTIVE

To screen immediate family members of thalassaemia patients for carrier identification and counselling.

METHODS

The cross-sectional study was conducted at an urban thalassaemia treatment and prevention centre in Karachi, Pakistan, from January to December 2008, and involved 188 siblings of 100 thalassaemia patients. Complete blood count, including haemogram, was performed in the siblings. Samples with MCV < 75fl and MCH < 25% were subjected to haemoglobin-electrophoresis. Haemoglobin A2 of 3.5% to 7.0% was labelled as beta-thalassaemia minor. Those with haemoglobin A2 of 3.0-3.4% but red blood cell count of > 4.5 x 1012/L were reported as equivocal and were screened for iron deficiency anaemia and a repeat haemoglobin A2 estimation was done on high performance liquid chromatography. Equivocal results of the chromoatography were screened for thalassaemia mutation. Mean values along with standard deviation were worked out for relevant variables.

RESULT

Of the 188 subjects, there were 124 (66%) males and 64 (34%) females. The mean age was 16.5 +/- 6.3 years (range: 3 months to 30 years) and the mean family size was 1.88 +/- 3.8 (range: 1-12) children per family. There were 51 (51%) first-cousin marriages in this group. Of the siblings, 65 (34.5%) were identified as normal, while 117 (62.2%) were reported as beta-thalassaemia carriers. Six asymptomatic siblings were reported as consistent with beta-thalassaemia major.

CONCLUSION

There were 62.2% siblings identified as beta thalassaemia carriers in the study as opposed to 5-8% carriers in the general population. We also identified six asymptomatic and unidentified cases of beta-thalassaemia intermedia in these families. Therefore, in our context where both resources and budgets are limited, it is practical to focus on siblings of identified thalasaemia patients.

HbA2 levels in normal, beta-thalassaemia and haemoglobin E carriers by capillary electrophoresis

OBJECTIVE

The capillary electrophoresis (CE) is a new system that utilizes the principle of electrokinetic separation of molecules in eight electrolyte buffer-filled silica capillaries. In this study, we established the normal ranges of haemoglobin A2 (HbA2) and haemoglobin F (HbF) levels for normal individuals using this system and also the HbA2 level in beta thalassaemia and haemoglobin E (HbE) individuals.

MATERIALS AND METHODS

154 samples from normal individuals, 218 samples from beta thalassaemia heterozygotes and 91 samples from HbE heterozygotes were subjected to high performance liquid chromatography (HPLC) and CE analysis.

RESULTS

The normal ranges for HbA2 and HbF by CE were 2.75% (SD 0.26%) and 0.03% (SD 0.24%) respectively, which were significantly lower than that of HPLC 2.88% (SD 0.25%) and 0.58% (SD 0.61%) (p < 0.001). The HbA2 level for HbE heterozygotes was 3.58% (SD 0.44%), which was significantly higher than normal (p < 0.001) but lower than that of beta-thalassaemia heterozygotes (p < 0.001) and the true HbE level was 24.28% (SD 3.38%).

CONCLUSION

The CE system provided a fully automated and high throughput system for haemoglobin analysis. We established the normal ranges for HbA2 and HbF levels by CE. We also determined the ranges for HbA2 in beta thalassaemia and HbE heterozygotes using this system.

[The value of MCV, MCH and HbA(2) in laboratory screening of thalassemia]

OBJECTIVES

To explore the roles of mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and hemoglobin A(2) (HbA(2)) in the laboratory screening of thalassemia, and to find optimal screening modality for different conditions.

METHODS

From September 2008 to May 2011, 1384 subjects underwent thalassemia screening at Department of Obstetrics and Gynecology of Nanfang Hospital. Of them, 1036 cases were diagnosed with thalassemia (408 α-thalassemia, 608 β-thalassemia, and 20 αβ compound thalassemia, thalassemia group) and 348 without thalassemia, non-thalassemia group. All subjects were screened respectively for MCV, MCH and HbA(2). Analyses were performed in all subjects to assess the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy respectively associated with MCV, MCH and HbA(2) alone, combination of MCV and MCH, and combination of MCV, MCH and HbA(2).

RESULTS

(1) In the thalassemia group, the sensitivity of MCV alone was 92.9% (379/408) for α thalassemia, 99.3% (604/608) for β thalassemia and 100.0% (20/20) for αβ compound thalassemia. In the non-thalassemia group, the specificity of MCV alone was 75.0% (261/348). (2) In the thalassemia group, the sensitivity of MCH alone was 92.9% (379/408) in α thalassemia, 99.0% (602/608) in β thalassemia and 100.0% (20/20) in αβ compound thalassemia. In the non-thalassemia group, the specificity of MCH alone was 72.7% (253/348). (3) The sensitivity of Hb A(2) alone was 67.4% (275/408) for α thalassemia, 97.5% (593/608) for β thalassemia, and 100% (20/20) for αβ compound thalassemia while it's specificity was 72.4% (252/348) in the non-thalassemia group. (4) With positive indexes of MCV, MCH and MCV + MCH, when HbA(2) > 3.5% it had a high value in β-thalassemia screening, but when HbA(2) < 2.5% it had little value in α-thalassemia screening. (5) As a single marker, MCV and MCH had better sensitivity, specificity, positive predictive value, negative predictive value and diagnosis accuracy than HbA(2). MCV + MCH was the best for overall screening, but for β thalassemia screening, MCV + MCH + HbA(2) was the best.

CONCLUSIONS

MCV and MCH are suitable for epidemic screening in a large population, physical examination and premarital check-up. Hb electrophoresis and thalassemia gene diagnosis are recommended for subjects with positive MCV and MCH indexes. Diagnoses of α and β-thalassemia gene are recommended for pregnant women with positive MCV and MCH indexes.

The measurement of hemoglobin A2 and F in stored whole blood samples

BACKGROUND

Little information is available on the influence of the storage conditions on the results of hemoglobin A2 (HbA2) and F (HbF) testing.

METHODS

The stability of HbA2 and HbF was assessed on stored whole blood samples tested immediately after collection and after one week of storage at either + 4 degrees C or - 80 degrees C.

RESULTS

An excellent correlation was observed between fresh specimens and those stored at either + 4 degrees C (HbA2: r = 0.994; p < 0.001 and HbF: r = 0.999; p < 0.001) or - 80 degrees C (HbA2: r = 0.995; p < 0.001 and HbF: r = 0.999; p < 0.001). The mean biases from the reference fresh specimens were very modest for samples stored at + 4 degrees C (HbA2: -0.06%; HbF: 0.02%;) and - 80 degrees C (HbA2: - 0.06%; HbF: 0.05%).

CONCLUSIONS

The results of our investigation demonstrate that whole blood specimens for HbA2 and HbF testing can be stored at + 4 degrees C or - 80 degrees C for up to one week.

Sensitivity and specificity of simple erythrocyte osmotic fragility test for screening of alpha-thalassemia-1 and Beta-thalassemia trait in pregnant women

AIMS

To evaluate the validity of new simple qualitative osmotic fragility test (simple OF) as a screening test in predicting thalassemia trait (alpha-thalassemia-1 and beta-thalassemia).

METHODS

This diagnostic test study was conducted on non-anemic pregnant women attending antenatal care clinic, Maharaj Nakorn Chiang Mai Hospital, during September 2007, and June 2008. Blood samples were collected from 477 singleton pregnancies with no obvious medical complication such as iron deficiency anemia. Simple OF was performed in the same day, using 0.45% glycerin saline solution instead of saline solution. Quantitative HbA2 test and PCR (SEA type) were performed as gold standard to confirm the diagnosis of beta-thalassemia trait and alpha-thalassemia-1 trait, respectively. The main outcome measures included sensitivity, specificity, positive and negative predictive value of simple OF.

RESULTS

The simple OF test had very high sensitivity of 100%, specificity of 73%, positive and negative predictive value of 35, and 100%, respectively.

CONCLUSION

The new simple OF test (using 0.45% glycerin) has high sensitivity in detection of alpha-thalassemia-1 trait or beta-thalassemia trait and due to its simplicity, rapidity, availability and very low cost it may, therefore, be considered as a screening test in a large-scale population.

[Study on the incidence of beta-Thalassemia and genotypes among children under 7 year-olds in Nanning, Liuzhou and Baise areas, Guangxi province]

OBJECTIVE

To conduct research of beta-Thalassemia incidence and genotypes on children below 7 years of age in Nanning, Liuzhou and Baise areas, Guangxi province.

METHODS

A total of 2261 children aged below 7 in Nanning, Liuzhou and Baise areas were studied. Venous blood was detected by routine blood test, hemoglobin analysis and beta-Thalassemia genotyping.

RESULTS

Among 2261 samples, 125 showed high level of HbA2 and were diagnosed as beta-Thalassemia (5.53%). Genotypes of the patients were classified as: 59 cases with beta-globin gene condon (CD) 41-42 mutation, 33 cases CD17 mutation, 18 cases with TA TA box nt-28 mutation, 7 with IVS-II-654 mutation, 3 with CD43 mutation, 3 with HbE mutation, one with CD71-72 and TATA box nt-29 mutation, respectively. The genotyping frequencies of beta-Thalassemia were as follows: 47.20% for CD41-42 mutation, 26.40% for CD17 mutation, 14.40% for TATAbox nt-28 mutation, 5.60% for IVS-II-654 mutation, 2.40% for CD43 mutation, 2.40% for HbE mutation, 0.80% for CD71-72 mutation and TATAbox nt-29 mutation respectively.

CONCLUSION

This study on children in the area with high incidence of beta-Thalassemia reflected the incidence and characteristics of genotypes in this area. Our data also provided evidence for the development of a program on genetic counseling and prevention for thalassemia.

Identification of a New δ Chain Hemoglobin Variant in a β-Thalassemia Carrier: Hb A2-MUMC [δ13(A10)Ala → Asp]

We describe a case of beta-thalassemia (thal) trait in which the patient also carries a novel delta chain variant due to a missense mutation at amino acid codon 13 (GCC-->GAC, Ala-->Asp). The level of Hb A2 was not elevated, raising the potential for misdiagnosis.

A Novel β-Thalassemic Allele Due to a Two Nucleotide Deletion: β76 (−GC)

We have identified and characterized a novel beta-thalassemic mutation in a North African adult. The molecular defect consists of a two nucleotide (nt) deletion in the beta-globin gene at codon 76 [beta76 (-GC), c.229-230delGC]. This frameshift mutation generates a TGA stop codon at position 89. The carrier presented with mild microcytic anemia (Hb 12.8 g/dL, MCV 60 fL), no detectable Hb F, an elevated Hb A2 level (5.5%) with no other mutation in the beta-globin gene and none of the more common known deletions in the alpha-globin cluster. No abnormal hemoglobin (Hb) was present in routine electrophoresis or in high performance liquid chromatography (HPLC) analyses. Pathologic inclusions were absent in both mature red cells and in reticulocytes. This observation reinforces the hypothesis that nonsense and frameshift mutations that result in a premature stop codon in exon 1 or exon 2 inherited in the heterozygous state do not generate dominant beta-thalassemia (thal). This is the first example of a premature stop codon at position 89.

δ-Thalassemia in Cyprus

To help clarify the hematological picture of patients who may be positive for beta- and delta-globin gene mutations, the following study was carried out. Our aim was to identify the delta-globin gene mutations found in the Greek Cypriot population, their frequencies and the Hb A2 values associated with them. Seventy-four samples were selected from a random sample of 5,030 individuals, and the database of the Molecular Genetics Thalassaemia Department containing diagnostic analyses data was also mined for relevant information. Four novel for Cyprus delta-globin gene mutations: -30 (T-->C), Hb A2-Wrens [delta98(FG5)Val-->Met, GTG-->ATG], IVS-I-2 (T-->C) and Hb A2-Yokoshima [delta25(B7)Gly-->Asp (GGT-->GAT)] were identified. Hb A2-Yialousa [delta27(B9)Ala-->Ser, GCC-->TCC], Hb A2-Yokoshima, Hb A2-Troodos [delta116(G18)Arg-->Cys, CGC-->TGC], Hb A2-Pelendri [delta141(H19)Leu-->Pro, CTG-->CCG], codon 4 [delta4(A1)Thr-->Ile], codon 59 (-A), Hb A2-Wrens, IVS-II-897 (A-->G), IVS-I-2, -55 (T-->C) and -30 bring the total to 11 delta-globin alleles found in the Greek Cypriot population. Hb A2-Yialousa is the most common mutation followed by codon 4, with frequencies of 60.7 and 17.8%, respectively.Hb A2 levels above 1.9% have been found to indicate a significantly reduced possibility for the presence of a delta-globin gene mutation in this population. For Hb A2 levels of 1.7 and 1.8% the possibility of a delta-globin gene mutation rises to 90.9% and reaches 100% for lower Hb A2 levels. The frequency of all the mutant delta-globin chromosomes in the sample is 0.0067 and the carrier frequency is 1.26%.

High Hb A2β-Thalassemia Due to a 468 bp Deletion in a Patient with Hb S/β-Thalassemia

We describe a case of Hb S/beta-thalassemia (thal) involving a 468 bp deletion that removes the beta-globin gene promoter but leaves the coding regions intact. This is the second report of this deletion, and our family study establishes that this deletion causes beta0-thal with unusually high levels of Hb A2 and Hb F. As with other genotypes involving deletions of the 5' region of the beta-globin gene, our patient had a mild form of Hb S/beta-thal.

Sensitivity and specificity of mean corpuscular hemoglobin (MCH): for screening alpha-thalassemia-1 trait and beta-thalassemia trait

OBJECTIVE

To evaluate sensitivity, specificity, and positive and negative predictive value of mean corpuscular hemoglobin (MCH) for screening alpha-thalassemia-1 trait and beta-thalassemia trait.

MATERIAL AND METHOD

Descriptive analysis, diagnostic test, was conducted on 396 pregnant women attending the antenatal clinic between September 2007 and June 2008. Blood samples were collected from pregnant women after counseling and getting informed consent. MCH was measured in all samples by automated hematology analyzer Determination of HbA2 level for diagnosis of beta-thalassmia trait and PCR for alpha-thalassemia-1 gene (SEA type) were performed in all cases as a gold standard The data were collected and analyzed for sensitivity, specificity, and positive and negative predictive value of MCH for screening alpha-thalassemia-1 trait and beta-thalassemia trait.

RESULTS

Based on the ROC curve, the best cut-off level of MCH in predicting the thalassemia carriers was 26.5 picrograms. Positive MCH (< 26.5 picrograms) gave the sensitivity of 95.2% and specificity of 82.3% in screening alpha-thalassemia-1 trait and beta-thalassemia trait. The positive predictive value and negative predictive value were 40.4% and 99.3% respectively.

CONCLUSION

MCH is a good tool for screening alpha-thalassemia-1 trait and beta-thalassemia trait during pregnancy because of its simplicity, low cost, (when determined as a part of complete blood count), and high sensitivity.

[Epidemiological investigation and genotype of thalassemia on middle school students in Chongzuo, Guangxi]

OBJECTIVE

To investigate the carrier ratio and the genotype of thalassemia among students of secondary school in Chongzuo, Guangxi.

METHODS

From June 10-20, 2008 among 7 regions of Chongzuo, 1 secondary school was randomly chosen from each region, and the number of student volunteers was determined by 0.5 per thousand proportion of the local population size. 1097 students were screened, including 515 boys and 582 girls of 12-16 year olds. Among them, 968 cases were Zhuang (438 boys and 530 girls) 128 cases were Han (76 boys and 52 girls) and one case was Yao nationalities (boy). Analysis of blood cells was detected by Cell Dyn 1700 automatic hemocyte analysator while hemoglobin F (HbF) and hemoglobin A2 (HbA2) were detected by hemoglobin autoanalyse variant. Among those with HbA > or = 4% that belonged to beta-thalassemia before alpha and beta-thalassemia gene were analyzed to identify the genotypes. If HbA2 was <4% but MCV< or = 80 fl, alpha-thalassemia gene was analyzed.

RESULTS

Among 1097 cases, 218 were alpha-thalassemia (19.87%), 50 were beta-thalassemia (4.56%) and 13 were combination of alpha beta-thalassemia (1.19%). The overall detected ratio was 25.62%. 133 cases with thalassemia were boys (25.83%) and 148 were girls (25.43%) with no significant difference (P>0.05). 255 cases of thalassemia were Zhuang (26.34%), and 25 were Han nationality (19.52%). The detected ratio among Zhuang nationality was higher than in Han nationality and with significant difference statistically (P<0.01). 3 kinds of deletion (-alpha(3.7)/, -alpha(4.2)/, --(SEA)/) and another 3 kinds of non-deletion (alpha alpha(CS)/, alpha alpha(WS)/, alpha alpha(QS/) alpha-thalassemia genotype were identified, with a higher rate of alpha alpha(WS)/. Among the beta-thalassemia genotype, CD41-42 appeared the most common genotype. MCV of thalassemia was lower than in the controls, with significant difference (P<0.01). 78-90 fl of alpha-thalassemia was detected from the MCV specimen. If taken MCV<79 fl as the positive phenotype of thalassemia, 32 cases were misdiagnosed. The rate of missed diagnosed cases was 2.97%.

CONCLUSION

Rate of thalassemia carrier among students of secondary school in Chongzuo, Guangxi was considered to be high, especially those belonged to Zhuang nationality were higher than the Hans. The carrier rate of alpha alpha(WS)/ was higher, with CD41-42 the most common genotype.

Comparison of fast protein liquid chromatography (FPLC) with HPLC, electrophoresis & microcolumn chromatography techniques for the diagnosis of beta-thalassaemia

BACKGROUND & OBJECTIVE

beta-thalassaemia is a genetic disorder and an important health problem around the world. Quantitative haemoglobin A(2) (HbA(2)) levels are used for the diagnosis of beta-thalassaemia. The conventional methods are high performance liquid chromatography (HPLC), electrophoresis, and microcolumn chromatography techniques. We established a fast protein liquid chromatography (FPLC) method, to measure quantitatively of HbA(2) levels, and compared its efficacy with conventional methods.

METHODS

The FPLC method, using a DEAE Sepharose, Hi Trap anion-exchange column chromatography technique was set up for HbA(2) measurement. In this study, 220 blood samples were screened for haemoglobin type by FPLC technique and also using HPLC, microcolumn chromatography and electrophoresis.

RESULTS

The FPLC results were highly correlated (r = 0.985, P<0.001) with those of HPLC for quantification of HbA(2) as well as cellulose acetate electrophoresis (r = 0.977) and microcolumn chromatography (r = 0.980). The FPLC method showed 100 per cent sensitivity and specificity, positive and negative predictive value for beta-thalassaemia diagnosis. In addition, the FPLC method was simple, rapid, low cost and reproducible. The HbA(2)/E range of FPLC for beta-thalassaemia was 6-10 per cent, HbE trait was 10-40 per cent, beta-thalassaemia/HbE was 40-60 per cent and homozygous HbE was more than 60 per cent.

INTERPRETATION & CONCLUSION

Our findings suggested that FPLC method could be used as a cost-effective method for routine beta-thalassaemia diagnosis.

Beta thalassaemia trait in western Nigeria

BACKGROUND

Genes for thalassaemia, haemoglobin S, Glucose-6-phosphate dehydrogenase which confer resistance to malaria are found in high frequencies in Nigeria, 25% of the population being carriers of the sickle cell trait while another 25% are hemizygous for the G6PD gene. The frequency of alpha thalassaemia is equally high among Nigerians but there is little information on beta thalassaemia in this population. A recent study however suggest a high prevalence of beta thalassaemia in the same population, hence the need for this study.

METHODS

Haemoglobin A(2) and HbF were determined in healthy adults who have haemoglobin A genotype by elution after electrophoresis and alkaline denaturation methods respectively.

RESULTS

The mean HbA(2) among the subjects was 3.3% (range 2.0-5.6%) while the mean HbF was 2.6% (range 0.4-8.8%). Twenty-six percent of the subjects had HbA(2) values higher than 3.9% while 86% had HbF values greater than 1%, twenty-four percent had elevated HbA(2) and HbF. The mean HbA(2) value was 2.7% among those with HbF <1%, 3.6% among those with HbF 1-3% and 3.1% among those with HbF >3%.

CONCLUSION

These findings confirm that the frequency of beta thalassaemia in western Nigeria is higher than previously thought and that many of the individuals studied may be silent carriers of the beta thalassaemia trait. Its presence may also have been masked by the high prevalence of alpha thalassaemia in the same environment. It is therefore important to consider beta thalassaemia trait as a differential diagnosis in patients who present with haemolytic anaemia in this environment.

Evaluation of an automated capillary electrophoresis system in the screening for hemoglobinopathies

BACKGROUND

The biochemical diagnosis of hemoglobinopathies (thalassemias and hemoglobin (Hb) variants) is based on the separation and the quantification of Hb fractions. HPLC is the most commonly used method but capillary electrophoresis (CE) methods have also been developed successfully. The Capillarys II system is the first fully automated CE system that allows the quantification of Hb A2 and Hb F and the separation of Hb variants. We evaluated the ability of this system to separate and identify Hb variants and to quantify Hb A2 and Hb F.

MATERIAL AND METHODS

The separation of 18 different Hb variants was studied and the imprecision on migration times was calculated for the three most frequent ones. The total imprecision on Hb A2 and Hb F quantification was determined. The results obtained for 44 patients were compared with those given by HPLC. The interference on Hb A2 measurement due to the presence of Hb S was studied.

RESULTS

Fourteen out of the 18 variants tested, including all variants of clinical importance, were separated from Hb A. Imprecision on migration times was less than 1%. For Hb A2 quantification, imprecision was less than 3.5% and for Hb F, less than 7.0%. The comparison with HPLC showed an acceptable agreement between both methods but a systematic negative bias for Hb A2 and both proportional and systematic biases for Hb F. No interference from the presence of Hb S on the quantification of Hb A2 was observed.

CONCLUSIONS

The fully automated Capillarys Hemoglobin method allows the detection and the separation of the most common Hb variants. It provides also a precise, quick, and very easy quantification of Hb F and Hb A2, even in the presence of Hb S. It is very suitable for routine investigation of hemoglopinopathies.

Use of a low pressure liquid chromatography system for haemoglobinopathy screening

A closed low pressure liquid chromatography system (LPLC) is described which is suitable for haemoglobinopathy screening. The system (Glycomat) was originally developed for the quantitation of the glycated haemoglobin (HbA1). The same biochemical principles have been applied to the separation of haemoglobin A2 (HbA2) and haemoglobin variants. The instrument offers three modes of use including a fast haemoglobin elution, a variant screen and a HbA2 assay for thalassaemia screening. The fast screen isolates all of the common haemoglobin variants except HbE which elutes with HbA. This mode is a more rapid alternative to the Sickledex test. The variant screen produces a wider separation of abnormal variants giving an identification and quantitation for each. The HbA2 assay separates this minor fraction from all other haemoglobins giving an accurate percentage. Abnormal variants are also separated. To validate the HbA2 assay 252 samples were assayed by the cellulose acetate electrophoresis/elution method and LPLC with a correlation of 0.932. The system provides an accurate and sensitive alternative to traditional manual chromatography and electrophoresis methods. The automated sampler allows batches from 1-99 samples to be processed with significant savings in operator time.

Hemoglobin E disease in North Indian population: a report of 11 cases

Hemoglobin E (beta26Glu --> Lys) is the most common hemoglobin (Hb) variant in Southeast Asia and the second most prevalent worldwide. However in India, it is prevalent in Bengal and the north-eastern region, but relatively rare in the rest of the country. Identification of this Hb variant is important, because the doubly heterozygous state for HbE and beta-thalassemia is characterized clinically by thalassemia major, a situation different from other compound heterozygous states for structural beta-chain variants and beta-thalassemia. Thus, the affected individual may be symptomatic and transfusion dependent at an early age. This paper reports four cases with Hb E trait, three cases with hemoglobin E disease and another four cases with Ebeta-thalassemia. Laboratory investigations are based on RBC indices and high performance liquid chromatography (HPLC). A negative correlation has been found to exist between levels of HbA(2) and RBC indices including the MCV and MCH. A similar correlation has been seen between levels of HbF with Hb, RBC count, and MCV. The main aim is to increase the awareness of this relatively rare disorder, so that it can be included in the differential diagnosis of patients presenting clinically like thalassemia intermedia or thalassemia major. This awareness may also help in prenatal diagnosis, genetic counseling and clinical management. The clinical, hematological and laboratory features of this disorder are also discussed.

Usefulness of cell counter-based parameters and formulas in detection of beta-thalassemia trait in areas of high prevalence

The present study aimed to retrospectively evaluate the usefulness of cell counter-based parameters and formulas in beta-thalassemia trait (BTT) detection. The study included 170 BTT cases (hemoglobin [Hb]A(2) >4.0% [0.04]) and 30 non-BTT cases (HbA(2), 2.3%-3.5% [0.02-0.04]). Depending on the hemoglobin level and iron deficiency, the BTT group was further classified into classic BTT (n = 112) and BTT with iron deficiency anemia (n = 58). The RBC count, MCH, MCV, RDW, and Shine and Lal, Mentzler, Srivastava, England and Fraser, Ricerca, and Green indexes were applied. For the first time in the population of India, these 10 cell counter parameters and manual formulas were compared with high-performance liquid chromatography-derived HbA2 levels for deriving a cost-effective alternative method; and receiver operating characteristic curves were applied. We found that the Shine and Lal, Srivastava, and Mentzler indexes, MCV, and MCH have better discriminative function than the RBC count and red cell distribution width and their related formulas.

Quantification of Hemoglobin A2 by Tandem Mass Spectrometry

Background: Peptide-based analysis of whole blood using electrospray tandem mass spectrometry (MSMS) in multiple reaction monitoring (MRM) mode enables rapid detection and sequence confirmation of clinically significant hemoglobin (Hb) variants. We applied a similar, quantitative approach to the measurement of δ:β-globin peptide ratios as potential surrogate markers of HbA2, a biomarker used in population screening for β-thalassemia trait.

Methods: We studied 163 blood samples with normal HbA2 (%), 105 with increased HbA2, 43 with δ-chain variants, and 8 with Hb Lepore. All were tested by HPLC. The samples were also incubated with trypsin for 30 min at 37 °C for MSMS with flow injection analysis. MRMs for the δ- (T2, T3, and T14) and β- (T2, T3, and T13) globin tryptic peptides were acquired for 1 min, and δ:β peptide ratios were calculated. We used HPLC and MSMS to analyze 26 paired whole blood and dried blood spot samples after storage for 1, 8, and 29 days.

Results: Within- and between-assay imprecision values (CVs) were &lt;6.1% and &lt;8.4%, respectively, for the δ:β peptide ratios. Digests were stable at 10 °C for 6 days. Significant correlations (P &lt;0.0001) between MSMS δ:β-globin peptide ratios and HPLC HbA2 allowed differentiation between increased HbA2 concentrations and concentrations within the reference interval and identification of Hb Lepore. This differentiation was repeatable by MSMS, but not by HPLC, after blood spot samples had been stored for 1 month.

Conclusion: This study validates the quantitative δ:β-globin peptide ratio as a surrogate marker of HbA2 and demonstrates the potential of rapid peptide-based MSMS for multiplexed, high-throughput protein biomarker characterization and quantification.

Effect of HbS in the determination of HbA2 with the Biorad Variant II analyzer

OBJECTIVES

The effect of the presence of HbS in the determination of HbA2 using the Biorad Variant II analyzer.

DESIGN AND METHODS

The effect of HbS presence in the samples was quantified using the HELENA SAS-MX alkaline gel electrophoresis kit as the reference method.

RESULTS

The %HbA2 values from the Variant II analyzer and the HELENA SAS-MX alkaline gel electrophoresis kit show a good linear correlation in the absence of HbS. A strong positive bias in the %HbA2 values from the Variant II is apparent in the presence of HbS in the samples, when compared to the alkaline electrophoresis gel.

CONCLUSION

The Variant II analyzer gives reliable results for %HbA2 determination when no HbS is detectable in the samples. When HbS is present, the gel electrophoresis method gives more accurate results.

Increased haemoglobin A2 percentage in HIV infection: disease or treatment?

An elevated haemoglobin A2 percentage has been reported in HIV-infected patients, possibly attributable to therapy. In cross-sectional and cohort studies we have established that A2 is often elevated in untreated patients; a further rise during treatment is attributable specifically to zidovudine. The haemoglobin A2 may be high enough to lead to a misdiagnosis of beta thalassemia trait if there is a lack of awareness of this unexpected effect of HIV infection and its treatment.

Bias-corrected diagnostic performance of the naked-eye single-tube red-cell osmotic fragility test (NESTROFT): an effective screening tool for beta-thalassemia

It is being increasingly recognized that a majority of the countries in the thalassemia-belt need a cost-effective screening program as the first step towards control of thalassemia. Although the naked eye single tube red cell osmotic fragility test (NESTROFT) has been considered to be a very effective screening tool for beta-thalassemia trait, assessment of its diagnostic performance has been affected with the reference test- and verification-bias. Here, we set out to provide estimates of sensitivity and specificity of NESTROFT corrected for these potential biases. We conducted a cross-sectional diagnostic test evaluation study using data from 1563 subjects from Central India with a high prevalence of beta-thalassemia. We used latent class modelling after ensuring its validity to account for the reference test bias and global sensitivity analysis to control the verification bias. We also compared the results of latent class modelling with those of five discriminant indexes. We observed that across a range of cut-offs for the mean corpuscular volume (MCV) and the hemoglobin A2 (HbA2) concentration the average sensitivity and specificity of NESTROFT obtained from latent class modelling was 99.8 and 83.7%, respectively. These estimates were comparable to those characterizing the diagnostic performance of HbA2, which is considered by many as the reference test to detect beta-thalassemia. After correction for the verification bias these estimates were 93.4 and 97.2%, respectively. Combined with the inexpensive and quick disposition of NESTROFT, these results strongly support its candidature as a screening tool-especially in the resource-poor and high-prevalence settings.

Effect of HbS in the determination of HbA2 with the TOSOH HLC-723G7 analyzer and the HELENA Beta-Thal Quik column kit

OBJECTIVES

The analytical performance of the TOSOH HLC-723G7 hemoglobin HPLC analyzer and the effect of the presence of HbS in the determination of HbA(2) using HPLC and manual column methods.

DESIGN AND METHODS

The performance characteristics of the TOSOH HLC-723G7 analyzer in the determination of HbA(2) were compared to those of the HELENA Beta-Thal Quik column. The effect of HbS presence in the samples was quantified using the HELENA SAS-MX alkaline gel electrophoresis kit as the reference method.

RESULTS

Within-run and between-run CVs for HbA(2) were better for the TOSOH HPLC analyzer than for the HELENA manual column method. The presence of HbS in the samples produces a strong positive bias in the %HbA(2) values when using both the HPLC and manual column methods, compared to the alkaline electrophoresis gel.

CONCLUSION

Both the TOSOH HPLC and the manual column are reliable methods for %HbA(2) determination when no HbS is detectable in the samples. When HbS is present, the gel electrophoresis method gives more accurate results.

External quality assessment of hemoglobin A2 measurement: data from an Italian pilot study with fresh whole blood samples and commercial HPLC systems

BACKGROUND

To evaluate the extent of interlaboratory variation and accuracy in hemoglobin A(2) (HbA(2)) assays, a pilot study of external quality assessment was organized among 48 Italian laboratories routinely measuring HbA(2). As part of the study, a survey was also performed by sending a questionnaire concerning some important analytical aspects related to the determination of HbA(2).

METHODS

The trial specimens consisted of three whole blood samples (A, B and C) with normal, pathological and borderline HbA(2) content, respectively. All laboratories used HPLC analyzers from the same manufacturer (Bio-Rad Laboratories).

RESULTS

Normal and pathological samples were clearly differentiated by all laboratories, while data for the borderline sample partially overlapped those for the other samples. The overall interlaboratory coefficient of variation was 8.0%, 6.0% and 7.9% for samples with low, high and intermediate HbA(2) levels, respectively. To assign HbA(2) target values to the samples, the median of the laboratory group was used. The accuracy of HbA(2) results was evaluated on the basis of allowable total error. The proportion of laboratories reporting unacceptable results was 31.9% (15 out of 47) for sample A, 17.0% (8 out of 47) for sample B, and 31.9% (15 out of 47) for sample C. No abnormalities in the chromatographic separation pattern were reported by any of the laboratories.

CONCLUSIONS

We conclude that quality in the measurement of HbA(2) should be improved.

[Thalassemia beta in children from Pomerania Region]

The thalassemias are inherited disorders resulting from deficient synthesis of one or more polypeptide chains of normal haemoglobin. There are two main groups of thalassemia: alpha and more common beta. The carriage of thalassemia genes are widely spread and the disease is considered the most common genetic disorder worldwide. Thalassemias are particularly prevalent in inhabitants of Italy, Greece, Spain, Mediterranean Islands, West Africa and some parts of Asia. The most common thalassemia beta cases are characterized from asymptomatic to severe microcytic anaemia with hepatosplenomegaly and physical development disturbances. The authors present eight unrelated children from the Pomerania Region of Poland complaining of chronic microcytic anaemia with normal iron level. Elevated level of haemoglobin A2 and in some of them haemoglobin F revealed thalassemia beta.

Beta thalassemia IVS-I-5(G-->C) heterozygosity masked by the presence of HbJ-Meerut in a Dutch-Indian patient

We describe the genotype/phenotype correlation in a 35 year old anemic female referred to our laboratory because a fast eluting minor fraction on HPLC, mild hemolysis and hematological parameters suggesting a Thalassemia trait, eventually in combination with iron depletion. Direct sequencing of the alpha globin genes revealed heterozygosity for HbJ-Meerut, a Glu-->Ala substitution at residue 120 not justifying the hematological parameters. No other point mutations were found on the alpha genes and Gap-PCR excluded the 6 common deletion defects. Direct sequencing of the beta-globin genes revealed the IVS-I-5 (G-->C) transversion in absence of the elevated HbA2 levels usually measured in carriers of this beta-Thalassemia mutation. The HbA2 tetramer in the presence of HbJ-Meerut divides in two parts. One alphaN2/delta2 migrating on the right spot on HPLC. The other alphaJ2/delta2 migrating under the HbA fraction. Classic alkaline electrophoresis and the modern capillary electrophoresis CE showed these two tetramers and the reduction of the elevated HbA2 level of the beta-Thalassemia trait by at least 20% due to HbA2 Meerut.

Molecular characterization of beta-thalassemia in the Dohuk region of Iraq

beta-Thalassemia (thal) is an important health problem in the Dohuk region of northern Iraq because of its high carrier rate and the frequency of consanguineous marriages. Thus, the need to establish an effective preventative program is paramount. As part of this effort, we initiated this study to determine the molecular basis of this disorder in the region. For the latter purpose, either parent of 104 registered beta-thal major/intermedia patients had their full blood counts, hemoglobin (Hb) electrophoresis, Hb A2 and Hb F quantitation performed. Their DNA was extracted, amplified and reverse hybridized to specific oligonucleotide probes to detect 20 beta-thal mutations. The testing detected 12 beta-thalassemic mutations. The eight most frequent were: IVS-II-1 (G-->A), codon 44 (-C), codon 5 (-CT), IVS-I-1 (G-->A), codon 39 (C-->T), IVS-I-6 (T-->C), codons 8/9 (+G) and IVS-I-5 (G-->C). These mutations accounted for 81.7% of the thalassemic defects in the studied individuals. The less frequent mutations were: codon 8 (-AA), IVS-I-110 (G-->A), codon 30 (G-->C) and codon 22 (-7 bp), and the beta-thalassemic defects remained uncharacterized in 11.5% of cases. This is the first study of beta-thal mutations from Iraq, and shows a frequency of thalassemic defects different from those reported in surrounding countries. It provides a foundation for prenatal genetic testing that will be part of a thalassemia prevention program in the Dohuk region.