Unraveling Impact of Hemoglobin F and A2 Levels: Correlation With Disease Severity and Treatment Response in Transfusion-Dependent Beta-Thalassemia.

BACKGROUND: Fetal hemoglobin (HbF) has been reported to be associated with disease severity and treatment response to HbF-inducing therapies like Hydroxyurea and thalidomide in patients suffering from transfusion-dependent beta-thalassemia (TDT). However, the role of hemoglobin A2 (HbA2) remains less clear in TDT, therefore this study aims to determine the impact of both HbF and HbA2 levels on disease severity and treatment response. METHODOLOGY: A prospective observational study was conducted at the Peshawar Institute of Medical Sciences and Fatimid Foundation Peshawar from May 2023 to October 2023. A total of 232 TDT-diagnosed patients were enrolled using a convenient sampling technique, whereas coinheritance of beta-thalassemia with other hemoglobinopathies was excluded. RESULT: This study reveals a significant impact of HbF on disease severity (p<0.05) but finds no substantial correlation (p>0.05) between HbA2 levels and disease severity. Additionally, HbF and HbA2 levels exhibit no association with treatment response categories in patients receiving HbF induction therapy, and various mutations do not significantly alter HbF and HbA2 levels or disease severity parameters in TDT patients. CONCLUSION: The study established a significant association between HbF and disease severity. However, regarding treatment response, neither HbF nor HbA2 levels impact response categories. Combinatorial treatment with hydroxyurea and thalidomide showed superior efficacy compared to monotherapy. A larger sample size and extended follow-up are recommended to further explore the impact of HbF, HbA2, and various mutations on disease severity and treatment response.

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

OBJECTIVES: Accurate quantification of hemoglobin (Hb) A2 is vital for diagnosing ß-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 ß-thalassemia screening. Additionally, we prospectively evaluated the chosen cutoff value in 632 samples. Mutations in the ß- 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), ß-thalassemia (bias, -0.27; r, 0.927), and non-ß-thalassemia carriers (bias, -0.36; r, 0.928). An HbA2 cutoff value of ≥4.0 % for ß-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 ß-Hb variant, Hb La Desirade [HBB:c.389C>T], associated with ß-thalassemia and co-inherited with a single α-globin gene. CONCLUSIONS: The Premier Resolution HPLC is a reliable and accurate method for routine ß-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.

The Impact of Ca2+ on Intracellular Distribution of Hemoglobin in Human Erythrocytes.

The membrane-bound hemoglobin (Hb) fraction impacts red blood cell (RBC) rheology and metabolism. Therefore, Hb-RBC membrane interactions are precisely controlled. For instance, the signaling function of membrane-bound deoxy-Hb and the structure of the docking sites in the cytosolic domain of the anion exchanger 1 (AE-1) protein are well documented; however, much less is known about the interaction of Hb variants with the erythrocyte's membrane. Here, we identified factors other than O2 availability that control Hb abundance in the membrane-bound fraction and the possible variant-specific binding selectivity of Hb to the membrane. We show that depletion of extracellular Ca2+ by chelators, or its omission from the extracellular medium, leads to membrane-bound Hb release into the cytosol. The removal of extracellular Ca2+ further triggers the redistribution of HbA0 and HbA2 variants between the membrane and the cytosol in favor of membrane-bound HbA2. Both effects are reversible and are no longer observed upon reintroduction of Ca2+ into the extracellular medium. Fluctuations of cytosolic Ca2+ also impact the pre-membrane Hb pool, resulting in the massive transfer of Hb to the cellular cytosol. We hypothesize that AE-1 is the specific membrane target and discuss the physiological outcomes and possible clinical implications of the Ca2+ regulation of the intracellular Hb distribution.

Analysis of annual distributions of hemoglobin A2 values as a method to test for HbA2 standardization.

BACKGROUND AND AIMS: The monitoring of yearly distributions of HbA2 measured has been indicated as a reliable indicator of worldwide standardization. MATERIALS AND METHODS: Measurements/year of HbA2 have been collected over three consecutive years in 15 Italian laboratories each using the same analytical method over three years period. HbA2 distributions, cleaned of replicated measurements, were compared by the overlapping area of the raw probability density functions expressed by coefficient eta (η), and by comparing the reference intervals for the central part of each distribution estimated by the indirect method refineR using the R package "refineR". RESULTS: According to the overlapping areas analysis the distributions/year of the data provided by 4 centers able to perform at least 1000 measurements/year were similar in 2 consecutive years. Moreover, the reference intervals provided by 2 centers using the same analytical methods in two separate locations over the three consecutive years, were very similar. The highest overlap (99.7 %) was observed in one center over two consecutive years. The overlapping areas were very high (93.6-95.7%) in 8 out of 9 inter-comparisons. CONCLUSION: Despite the limitations of this study the yearly distribution of the HbA2 measured in various centers appears a reliable tool to test HbA2 standardization over different centers using different analytical methods.

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.

Effect of megaloblastic anemia on hemoglobin A2 and diagnosis of ß-thalassemia trait.

Context: ß-thalassemia trait is usually diagnosed by raised hemoglobin A2 (HbA2). The presence of megaloblastic anemia can cause an increase in HbA2 and create a diagnostic dilemma. Here, we have analyzed the effect of vitamin B12 and folic acid supplementation on HbA2 and diagnosis of ß-thalassemia trait in cases of megaloblastic anemia with raised HbA2. Materials and Methods: Cases of megaloblastic anemia with raised HbA2 on high-performance liquid chromatography (HPLC) were supplemented with vitamin B12 and folic acid. Post-treatment evaluation was done after 2 months. Cases showing adequate hematological response were subjected to statistical analysis. Based on post-treatment HbA2 value, the cases were diagnosed as normal, borderline raised HbA2, or ß-thalassemia trait. Pre- and post-treatment values of red cell parameters and HbA2 were analyzed. Results: There was a significant decrease in HbA2 value after vitamin B12 and folic acid supplementation. The diagnosis was changed in 70.97% of the cases after treatment. The chance of inconclusive diagnosis was decreased from more than 50% to less than 10%. Pre-treatment mean corpuscular volume (MCV) and HbA2% showed a significant difference between the thalassemic and normal groups. Conclusions: Megaloblastic anemia can lead to false-positive diagnosis of ß-thalassemia trait on HPLC. Repeat HPLC should be done after adequate supplementation of vitamin B12 and folic acid in cases of megaloblastic anemia with raised HbA2. Red cell parameters are not helpful to suspect ß-thalassemia trait in presence of megaloblastic anemia. However, HbA2% on HPLC can be a useful parameter to suspect or exclude ß-thalassemia trait in cases of megaloblastic anemia.

Impact of age-dependent red blood cell parameters on α-globin gene genotyping in children.

When screening for α-thalassemia in children, adult cut-offs for mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) are generally applied to guide genetic evaluation. However, the normal ranges for MCV and MCH are lower in children than in adults, so we hypothesized that using age-matched cut-offs could lead to a more rational diagnostic strategy. The aim of this study was to evaluate if age-matched cut-offs could be applied advantageously. Data on children referred to a hemoglobin fractionation at the Department of Clinical Biochemistry, Aarhus University Hospital between 2016-2021 were identified in the laboratory information system. α-globin gene (HBA1/HBA2) genotyping was performed using multiplex gap-polymerase chain reaction. A total of 387 children were identified. HBA1/HBA2-genotyping was performed in 207 children (53%), and α-thalassemia was diagnosed in 47 children (23%) with -α3.7/αα being the predominant genotype (13%). We found that 23 children had MCV and MCH levels in the normal age-matched range, and two of these children (9%) were α+ thalassemia carriers with three functional α-globin genes. Using age-specific cut-off levels resulted in a reduction of 23 (11%) genotypes performed. In conclusion, applying age-matched cut-offs for MCV and MCH when screening children for α-thalassemia lead to 11% fewer genotypes performed while 9% carriers of α+ thalassemia (of the medically innocuous genotype -α3.7/αα) would have been overlooked.

Erythrocyte Indices and Hemoglobin Analysis for α-Thalassemia Screening in an Area with High Carrying Rate.

Carriers of α-thalassemia exhibit hypochromic microcytosis with mean corpuscular volume (MCV) < 80 fL, mean corpuscular hemoglobin (MCH) < 27 pg, and reduced hemoglobin A2 (HbA2). We studied the distribution and diagnostic efficiencies of these indicators and their combinations in patients with and without alpha-thalassemia. Based on genetic diagnosis, 10,883 participants were divided into alpha-thalassemia group (n = 1655) and negative-for-alpha-thalassemia group (n = 9228). Erythrocyte parameters and hemoglobin analysis of the groups were analyzed. Moreover, we compared the four screening schemes (MCV/MCH, MCV/MCH/HbA2, MCV + MCH, MCV + MCH + HbA2) to find the best for α-thalassemia screening. The genotypes of --SEA/αα, and -α3.7/αα are the most prevalent with 54.9% and 27.6% in Fujian Province, China. There were significant differences in the distribution of MCV, MCH, and HbA2 in the two groups. Among the three, MCH exhibited the highest sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy. Although the four screening schemes have their advantages, there are significant differences in their sensitivity and specificity. MCV + MCH had the best diagnostic performance (72.6% sensitivity, 89.0% specificity) as well as the highest Youden index (61.59%). Our results showed that MCH could be used to screen α-thalassemia instead of MCV and HbA2. However, it is recommended that MCV/MCH/HbA2 screening be used in areas with high α-thalassemia incidence to increased sensitivity.

Thalassemia and erythroid transcription factor KLF1 mutations associated with borderline hemoglobin A2 in the Thai population.

INTRODUCTION: Elevated hemoglobin (Hb) A2 is an important diagnostic marker for ß-thalassemia carriers. However, diagnosis of cases with borderline Hb A2 may be problematic. We described the molecular characteristics found in a large cohort of Thai subjects with borderline Hb A2. MATERIAL AND METHODS: Examination was done on 21,657 Thai subjects investigated for thalassemia at Khon Kaen University, Thailand. A total of 202 subjects with borderline Hb A2 (3.5-4.0%) were selectively recruited and hematological parameters were recorded. DNA variants in α-, ß-, δ-globin, and Krüppel-like factor 1 (KLF1) genes were examined using PCR. RESULTS: Among 202 subjects, DNA analysis identified carriers of α+-thalassemia (n = 48; 23.8%), ß-thalassemia (n = 22; 10.9%) and KLF1 mutations (n = 48; 23.8%). No molecular defect was observed in the remaining 84 (41.5%) subjects. Interaction of KLF1 and α-thalassemia was observed in 10 cases. Of the 22 ß-thalassemia carriers, five ß+-thalassemia mutations were identified with lower MCV and higher Hb A2. Seven KLF1 mutations were detected in 10 genotypes in subjects with higher MCV and Hb F. No ß0-thalassemia, α-globin gene triplication or δ-globin gene mutation was detected. CONCLUSIONS: A large proportion of subjects with borderline Hb A2 are not ß-thalassemia carriers and for those with ß-thalassemia, only mild ß+-thalassemia mutations were detected. Evaluation of the patients using Hb A2, Hb F and MCV values will help in selecting cases for further molecular analysis. The results should explain the unusual phenotype of the cases and facilitate a thalassemia screening program in the region.

Microcytic Anaemia as Susceptibility Factors in Bipolar Spectrum Disorders: Review of the Literature, Replication Survey, and Co-Segregation within Families.

BACKGROUND: Potential interactions between mood disorders and microcytic anaemias have been suggested by case reports, surveys of haematological parameters in psychiatric populations, and surveys of psychiatric morbidity in thalassaemic carriers. OBJECTIVES: a) To review published studies.b) To study the prevalence of microcytic anaemia in a sample of Sardinian outpatients with recurrent mood disorders.c) To check whether mood disorders and microcytic anaemia co-segregate within families. METHODS: We extracted data on blood count and serum iron concentrations from the records of patients admitted between January 1st, 2001 and December 31st, 2016, to our clinic for mood disorders. Moreover, we studied siblings of subjects with both major mood disorders (according to Research Diagnostic Criteria) and heterozygous thalassaemia (according to Mean Corpuscular Volume, serum iron, and haemoglobin A2 concentrations). Siblings affected with a major mood disorder were examined for haematological concordance with the proband (reduced MCV and/or increased HbA2 in case of heterozygous ß-thalassaemia, or presence of gene deletions in case of α-thalassaemia). RESULTS: Microcytic anaemia was highly prevalent (81/337 = 24.0%) among outpatients with mood disorders. Starting from 30 probands with heterozygous ß-thalassaemia, concordance for reduced MCV and/or increased HbA2 was found in 78% (35/45) of affected siblings. Starting from 3 probands with heterozygous α-thalassaemia, only one of the 5 affected siblings carried four α-globin functional genes. CONCLUSION: Based on the review of the literature, the high prevalence of microcytic anaemia in outpatients, and the concordance between affected siblings, we can conclude that a role of heterozygous thalassaemias is highly probable. Future studies are required to establish the relevance of heterozygous thalassaemias and evaluate the magnitude of the effect, possibly using a molecular diagnosis also in the case of heterozygous ß-thalassaemia.

Screening of Some Indicators for Alpha-Thalassemia in Fujian Province of Southern China.

BACKGROUND: Carrier screening is the most effective means of controlling the prevalence of alpha-thalassemia. However, due to the differences in ethnic populations and genotypes, the distribution of mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and hemoglobin A2 (HbA2) varies in different regions. This study aimed to examine screening efficiency of these indicators in different genotypes of alpha-thalassemia in Fujian Province, China. METHODS: The data of 13,294 subjects collected from May 2016 to December 2019 were reviewed. The participants were categorized as alpha-thalassemia group and negative-for-alpha-thalassemia group based on the results of the genetic analysis. The distribution of MCV, MCH, and HbA2 in different groups was analysed statistically. And the screening efficiency of different indicators and schemes was compared in different genotypes. The positive criteria of MCV < 80fL, MCH < 27pg, and Hb A2< 2.5% were applied. RESULTS: Among the 13,294 subjects, 2658 were alpha-thalassemia carriers. The genotypes of -SEA/αα and -α3.7/αα are the most prevalent with 63.9% and 21.9% in Fujian Province, China. There were significant differences in the distribution of the three indicators in different groups. The detection rate of the three indicators combined screening was 92.6%. CONCLUSION: The distribution of the three indicators overlapped partly between alpha-thalassemia group and negative-for-alpha-thalassemia group. They showed significant differences in the median comparison of seven common genotypes. Combined screening with MCV, MCH and HbA2 improved the detection rate of alpha-thalassemia. The results of this study provide a data basis for clinical laboratories and a reliable reference for clinical consultation.

δ-Hemoglobinopathies in Thailand: screening, molecular basis, genotype-phenotype interaction, and implication for prevention and control of thalassemia.

The δ-globin gene defects are clinically silent but interaction with ß-thalassemia can lead to a misdiagnosis of ß-thalassemia carrier. We report an extensive molecular characterization of δ-hemoglobinopathies in Thailand. Study was done on 32,108 subjects, encountered at the thalassemia screening. Six different approaches based on the reduced Hb A2 or appearance of Hb A2-derivative were established for selective recruitment of subjects. Among 32,108 subjects, a total of 296 subjects were suspected of having δ-globin gene defects. Of these 296 subjects, Hb and DNA analyses identified δ-hemoglobinopathies with 10 different mutations in 34 (0.11%) of them. These included a novel mutation, [δCD30(AGG>GGG) (n = 1)], 5 previously undescribed in Thailand, [δ-44(G>A) (n = 7), Hb A2-Troodos (n = 5), δIVSII-897(A>C) (n = 4), δ-68(C>T) (n = 2), and Hb A2-Indonesia (n = 1)], and 4 mutations previously found in Thailand, [Hb A2-Melbourne (n = 9), δ-77(T>C) (n = 3), Hb A2' (n = 1), and Hb A2-Kiriwong (n = 1)]. Genetic heterogeneities seen included interactions of δ-globin gene defects with heterozygous Hb E, ß-thalassemia, α-thalassemia, and in cis locations of the Hb A2-Troodos and Hb E mutations found for the first time. Rapid identification methods of these δ-globin gene mutations were developed. The results should prove useful to a prevention and control program of hemoglobinopathies in the region.

Hemoglobins F, A2 , and E levels in Laotian children aged 6-23 months with Hb E disorders: Effect of age, sex, and thalassemia types.

INTRODUCTION: Determination of hemoglobins (Hbs) F, A2, and E is crucial for diagnosis of thalassemia. This study determined the levels of Hbs F, A2, and E in children aged 6-23 months and investigated the effect of age, sex, and types of thalassemia on the expression of these Hbs. METHODS: A total of 698 blood samples of Laotian children including 272 non-Hb E, 271 Hb E heterozygotes, and 155 Hb E homozygotes were collected. Hb profiles were determined using the capillary zone electrophoresis. Coinheritance of α-thalassemia and the homozygosity for Hb E mutation were checked by PCR-based assay. RESULTS: Children heterozygous and homozygous for Hb E had significantly higher Hb F and A2 levels than non-Hb E children (median Hb F = 1.1% for non-Hb E group, 2.7% for Hb E heterozygotes, and 9.4% for Hb E homozygotes; median Hb A2  = 2.6% for non-Hb E group, 3.8% for Hb E heterozygotes, and 5.2% for Hb E homozygotes). The median Hb E levels were 21.9% for Hb E heterozygotes and 85.3% for Hb E homozygotes. Comparing within group, there was a statistically significant difference between children with and without an α-gene defect for Hb A2 and E, but not Hb F. Based on a multiple regression analysis, age and sex were significantly associated with the expression of Hb F and A2 but not Hb E. CONCLUSIONS: Our findings can guide the development of a diagnostic approach to thalassemia in children aged 6-23 months.

Intraocular pressure in subjects with beta-thalassemia minor / Pressão intraocular em indivíduos com talassemia beta minor

ABSTRACT Purpose: Beta-thalassemia minor, a common hereditary blood disorder in Mediterranean countries such as Turkey, is associated with insulin resistance. Insulin resistance, in turn, can be associated with excessively high intraocular pressure and, therefore, intraocular pressure-induced blindness. This study aimed to investigate the intraocular pressure in subjects with beta-thalassemia minor. Methods: We conducted a cross-sectional study comprising of 203 subjects divided into two groups: beta-thalassemia minor (103) and healthy (100).Hemoglobin electrophoresis was performed and complete blood count, blood pressures, serum fasting glucose and insulin levels were measured. All subjects underwent ophthalmological examinations including intraocular pressure measurements. Results: Intraocular pressure in the subjects with beta-thalassemia minor was significantly lower than that in healthy subjects (p=0.007). Additionally, intraocular pressure was inversely correlated with hemoglobin A2 levels (p=0.001, r=-0.320). Serum insulin and systolic blood pressure were significantly higher in subjects with beta-thalassemia minor (p=0.03, p=0.009, respectively). Conclusion: Subjects with beta-thalassemia minor had lower intraocular pressure than healthy controls, suggesting beta-thalassemia minor may actually protect against high intraocular pressure.

RESUMO Objetivo: Beta-talassemia menor é uma doença hereditária comum no sangue em países mediterrâneos como a Turquia e está associada à resistência à insulina. A resistência à insulina por sua vez, pode estar associada à pressão intraocular excessivamente alta e, portanto à cegueira induzida pela pressão intraocular. Este estudo teve como objetivo investigar a pressão intraocular em indivíduos com beta-talassemia menor. Métodos: Foi realizado um estudo transversal compreendendo 203 indivíduos divididos em 2 grupos: beta-talassemia menor (103) e saudável (100). Eletroforese de hemoglobina foi realizada e hemograma completo, pressão arterial, glicemia em jejum e níveis de insulina medidos. Todos os indivíduos foram submetidos foram submetidos a exames oftalmológicos, incluindo medidas de pressão intraocular. Resultados: A pressão intraocular nos indivíduos com beta-talassemia menor foi significativamente menor do que em indivíduos saudáveis (p=0,007). Além disso, a pressão intraocular foi inversamente correlacionada com os níveis de hemoglobina A2 (p=0,001, r=-0,320). Insulina sérica e pressão arterial sistólica foram significativamente maiores em indivíduos com beta-talassemia menor (p=0,03, p=0,009, respectivamente). Conclusão: Os indivíduos com beta-talassemia menor tiveram pressão intraocular menor do que os controles saudáveis, sugerindo que a beta-talassemia menor pode, na verdade, proteger contra a alta pressão intraocular.

Identificación de &-talasemia en anemias microcíticas hipocrómicas refractarias al tratamiento con hierro en Nicaragua / Identification of &-thalassemia in hypochromic microcytic anemias refractory to iron treatment in Nicaragua

Resumen Justificación y objetivo: gran parte de los casos descritos de anemias microcíticas-hipocrómicas corresponden a anemias ferropénicas y síndromes talasémicos. El diagnóstico diferencial se complementa con pruebas de laboratorio como el hierro sérico, ferritina, entre otras; sin embargo, estas son de baja disponibilidad en países en vías de desarrollo. En Nicaragua, el diagnóstico de estas patologías se basa en el historial clínico y análisis hematológicos de rutina. El objetivo de este trabajo fue la implementación de la técnica de cuantificación de hemoglobina A2 en el diagnóstico clínico de β-talasemia. Métodos: se realizó un estudio transversal con 30 pacientes que mostraban microcitosis e hipocromía después de 3 meses de tratamiento con sales de hierro. Se realizó electroforesis de hemoglobina y se utilizó el kit de la casa comercial Beta-Thal HbA2 Quik Column para cuantificar la hemoglobina A2 en cada paciente. El análisis estadístico utilizado fue la prueba de t de student. Se consideraron significativas las diferencias a p<0,05. Esta investigación respetó los principios éticos que conciernen. Se contó con la aprobación del Comité de Ética Institucional, UNAN-Managua. Los participantes dieron su consentimiento informado. Resultados: al aplicar el método para cuantificación de hemoglobina A2, se obtuvo que el 67 % de las muestras presentaron una concentración de hemoglobina A2 mayor al valor de referencia establecido (3,3 %), siendo pacientes diagnosticados para β-talasemia menor. El 33 % restante presentó valores normales de hemoglobina A2 con microcitosis e hipocromía. Se encontraron diferencias estadísticamente significativas entre las medias de glóbulos rojos, volumen corpuscular medio, hemoglobina corpuscular media y hemoglobina A2, entre ambos grupos. Conclusión: el diagnóstico diferencial de anemias microcíticas hipocrómicas refractarias al tratamiento con hierro, se realiza inicialmente por el historial clínico del paciente, pero es necesario contar con pruebas diagnósticas como la cuantificación de hemoglobina A2 que permitan identificar las diversas patologías que cursan con microcitosis e hipocromía.

Abstract Justification and objective: much of the described cases of microcytic-hypochromic anemias are ferropenic anemias and Thalassemia syndromes. The differential diagnosis is complemented by laboratory tests as serum iron, ferritin, among others; However, these are of low availability in developing countries. In Nicaragua, the diagnosis of these diseases is based on clinical history and routine blood analysis. The objective of this work was to implement a technique for quantification of hemoglobin A2 in the clinical diagnosis of β-Thalassemia. Methods: We conducted a cross-sectional study with 30 patients showing hypochromia and microcytosis after 3 months of treatment with iron salts. Hemoglobin electrophoresis was performed, a kit from Beta-Thal HbA2 Quik Column was used to quantify the hemoglobin A2 in each patient. The statistical analysis used was the student's t test. The differences were considered significant at p < 0.05. This research respected ethical principles that concern. It had the approval of the committee of ethics institutional, UNAN-Managua and the participants gave their informed consent. Results: when applying the method for quantification of hemoglobin A2, 67% of samples presented a concentration of hemoglobin A2 greater than the reference value set at 3.3%, these patients were diagnosed with β-Thalassemia minor. The remaining 33% presented normal values of hemoglobin A2 with hypochromia and microcytosis. Statistically significant differences between the averages of red blood cells, mean corpuscular volume, mean corpuscular hemoglobin and hemoglobin A2 between the two groups was observed. Conclusion: The differential diagnosis of microcytic hypochromic anemias refractory to treatment with iron, is initially performed by the clinical history of the patient, but it is necessary to have diagnostic tests such as the quantification of hemoglobin A2, which allow the identification of patients with β-Thalassemia minor within this group. In our study 67% of the studied samples were identified as β-Thalassemia minor.

Determination of HbA2 by quantitative bottom-up proteomics and isotope dilution mass spectrometry.

BACKGROUND: Poor comparability between laboratories is often observed in the measurement of HbA2. A measurement procedure of higher metrological order is needed for value assignment to a reference material that shall be used as primary calibrator. METHOD: A reference measurement procedure has been developed based on isotope dilution mass spectrometry (IDMS). The α- and δ- subunits are quantified by signature peptides released by tryptic digestion of a 25 µL-blood sample. Full length U-15N-labeled HbA0 and HbA2 are used as internal standards and added to the sample at concentrations closely matching the levels of the natural forms in blood. By this, an improvement in precision could be achieved with respect to previous mass-spectrometry based methods. RESULTS: Recovery of HbA2 added to a blood sample was within 102.6-105.2%. Repeatability and within-laboratory imprecision was <2.0% for two blood samples containing HbA2 at a low and a high fraction. Total combined measurement uncertainty is estimated as 5.5%. Good agreement (r = 0.998) of results was obtained in a comparison of two laboratories using the described IDMS procedure. There is good correlation between commercial analytical systems and IDMS (r = 0.975-0.989). Some of the platforms provide significantly biased results, however, which potentially could be mitigated by reference to IDMS. CONCLUSION: IDMS holds a promise to be suitable as a reference measurement procedure for standardization of HbA2-measurements in laboratory medicine.

The shortcut strategy for beta thalassemia prevention.

We propose antenatal blood tests using high-resolution DNA melting (HRM) analysis for beta thalassemia mutation detection after hemoglobin A2 estimation as a modified strategy for the identification of beta thalassemia at-risk couples. Antenatal blood samples of 1,115 couples were transferred from the antenatal care clinic. Hemoglobin A2 was quantified, and proportions ≥3.5% were further assessed for beta thalassemia mutation using HRM analysis. Twelve types of beta thalassemia mutations, including hemoglobin E, were identified. There were 23 couples who were detected as at-risk. All at-risk couples were identified within 7 working days after sample receipt. Prenatal diagnosis revealed 6 affected fetuses. One fetus was homozygous CD17 (AT), and five fetuses exhibited beta0 - thalassemia/hemoglobin E disease. These results were consistent with the outcomes calculated using the Hardy-Weinberg equation. Antenatal blood tests for mutation detection using high-resolution DNA melting analysis after hemoglobin A2 estimation is a feasible laboratory method for the recruitment of couples with a fetus that is at risk for beta thalassemia. This modified strategy is cost-effective and may be beneficial for use in a beta thalassemia prevention program.