Erythrocyte indices in a large cohort of β‐thalassemia carrier: Implication for population screening in an area with high prevalence and heterogeneity of 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.

Molecular understanding of unusual HbE-β+-thalassemia with Hb phenotype similar to HbE heterozygote: simple and rapid differentiation using HbE levels

BACKGROUND

Low HbF expression in HbE-β+-thalassemia may lead to misdiagnosis of HbE heterozygosity. We aimed to characterize the β- and α-globin genes and the modifying factors related to HbF expression in patients with an Hb phenotype similar to that of HbE heterozygotes. Furthermore, screening tools for differentiating HbE-β+-thalassemia from HbE heterozygotes have been investigated.

PARTICIPANTS AND METHODS

A total of 2133 participants with HbE and HbA with varying HbF levels were recruited. Polymerase chain reaction-based DNA analysis and sequencing were performed to characterize β- and α-globin genes. DNA polymorphism at position -158 nt 5' to Gγ-globin was performed by XmnI restriction digestion. Receiver operating characteristic (ROC) curves were constructed using the area under the curve (AUC). Cutoff values of HbA2, HbE, and HbF levels for the differentiation of HbE-β+-thalassemia from HbE heterozygotes were determined.

RESULTS

Five β+-thalassemia mutations trans to βE-gene (β-87(C>A), β-31(A>G), β-28(A>G), β19(A>G), and β126(T>G)) were identified in 79 patients. Among these, 54 presented with low HbF levels, and 25 presented with high HbF levels. ROC curve analysis revealed an excellent AUC of 1.000 (95% confidence interval:1.000-1.000) for HbE levels, and a cut-off point of ≥35.0% had 100.0% sensitivity, specificity, and Youden's index for differentiating HbE-β+-thalassemia from HbE heterozygotes. The proportion of α-thalassemia mutations was 46.3 and 8.0% among HbE-β+-thalassemia patients with low and high HbF levels, respectively. Two rare α-thalassemia mutations (Cap +14(C>G) and initiation codon (ATG>-TG)) of α2-globin genes were identified. The genotype and allele of the polymorphism at -158 nt 5' to Gγ-globin was found to be negatively associated with HbF expression.

CONCLUSIONS

HbE-β+-thalassemia cannot be disregarded until appropriate DNA analysis is performed, and the detection of α-thalassemia mutations should always be performed under these conditions. An HbE level ≥35.0% may indicate screening of samples for DNA analysis for HbE-β+-thalassemia diagnosis.

Predicting thalassemia using deep neural network based on red blood cell indices

BACKGROUND AND OBJECTIVE

The traditional statistical screening method for thalassemia based on red blood cell (RBC) indices is being replaced by machine learning. Here, we developed deep neural networks (DNNs) that outperformed the traditional method for predicting thalassemia.

METHOD

Using a dataset of 8693 records comprising genetic tests and other 11 features we constructed 11 DNN models and 4 traditional statistical models and then compared their performances and analysed feature importance for interpreting DNN models.

RESULTS

The area under the receiver operating characteristic curve, accuracy, Youden's index, F1 score, sensitivity, specificity, positive predictive value and negative predictive value, were 0.960, 0.897, 0.794, 0.897, 0.883, 0.911, 0.914, and 0.882, respectively, for our best model, and compared with the traditional statistical model based on the mean corpuscular volume, these values were increased by 10.22%, 10.09%, 26.55%, 8.92%, 4.13%, 16.90%, 13.86% and 6.07%, respectively, and by 15.38%, 11.70%, 31.70%, 9.89%, 3.05%, 22.13%, 17.11% and 5.94%, respectively, for the mean cellular haemoglobin model. The DNN model performance will reduce without age, RBC distribution width (RDW), sex, or both WBC and PLT.

CONCLUSIONS

Our DNN model outperformed the current screening model. In 8 features, RDW and age were the most useful, followed by sex and the combination of WBC and PLT, the remaining nearly useless.

Evaluation of intervention strategy of thalassemia for couples of childbearing ages in Centre of Southern China

BACKGROUND

To describe the free intervention strategy of thalassemia for childbearing couples in Guangzhou.

METHODS

Routine hematology examinations were conducted for 137,222 couples. Among them, 37,501 couples who had mean corpuscular volume (MCV) <82 fL or mean corpuscular hemoglobin <27 pg were elected for Hb analysis and the deletions of four common α-thalassemia mutation. Reverse dot blot for common nondeletional α-thalassemia and β-thalassemia was selectively used. Three thousand twenty-two couples randomly selected were offered all those tests as a control group. Sanger sequencing, multiplex ligation-dependent probe amplification and next-generation sequencing were used for rare thalassemia. High-risk couples were offered prenatal diagnosis at 10-13 weeks' gestation based on informed consent.

RESULTS

The carrier rates of α-, β-, and αβ-thalassemia and δβ thalassemia/deletional HPFH were 7.7%, 3.02%, 0.5% and 0.059% respectively. Of them, 1.37% were identified as at-risk couples and 345 couples terminated the pregnancy. No severe α- and β-thalassemia births were observed. In the control group, two β- thalassemia carriers and one case with -α^3.7 /αα^QS were misdiagnosed, but all at-risk couples were found, and we could save 1,523,774 ¥ using our strategy. The cut-off points of 73.46 fL and 23.25 pg would be useful to find -α⁺ /α^T thalassemia.

CONCLUSION

The intervention strategy was cost-effective and offered reference in population thalassemia screening.

Prevalence and molecular spectrum of α- and β-globin gene mutations in Hainan, China

This study investigated prenatal diagnosis of α-thalassemia and β-thalassemia in 3049 families in 18 regions of Hainan Province. Molecular diagnosis was performed in 3049 couples with thalassemia in Hainan Province. Genomic DNA was extracted from peripheral blood of the couples and villus, amniotic fluid, or cord blood of fetuses. DNA-based diagnosis was performed using polymerase chain reaction. The most commonly detected mutation for α-thalassemia was- SEA/αα (31.53%), followed by - α4.2/αα (11.15%) and - α3.7/αα (11.02%). The most common mutation for β-thalassemia was CD41/42 (30.27%), followed by - 28 (2.56%). Prevalence was highest in the coastal regions and lowest in the Wenchang, Lingao, and Ding'an regions. We also found that the most common gene mutations in Han people and other minority groups were not homogeneous. Prenatal diagnosis showed 556 normal fetuses, 116 with α-thalassemia hydrops, and 134 with β-thalassemia major. Our findings provide important information for clinical genetic counseling regarding prenatal diagnosis for thalassemia major in Hainan Province.

Results from 8 years of the proficiency testing program for diagnosis of hemoglobinopathies under the prevention and control program of thalassemia in Thailand

INTRODUCTION

Hemoglobin (Hb) analysis is a key testing for diagnosis of hemoglobinopathies. Accurate analysis, interpretation of results, and genetic risk assessment are important. We report on 8 years of the proficiency testing (PT) program for hemoglobinopathies in Thailand.

METHODS

Laboratory participants were required to test two simulated PT items in each cycle using capillary electrophoresis, one was a husband and another was his pregnant wife. Related hematological parameters were provided. The participants also provide interpretation and evaluate the risk of having three severe thalassemia diseases in an expected fetus. Three cycles were operated per year in accordance with the ISO17043 and ISO13528 guidelines. A total of 84 laboratories throughout Thailand were participated.

RESULTS

A total of 24 PT cycles were performed during 2012-2019. Most participants had Excellent performance for the PT items with normal, β-thalassemia trait, hemoglobin E trait, hemoglobin E trait with α-thalassemia, and Hb H disease. However, when the PT items with homozygous Hb E and Hb E-β-thalassemia were tested, an increase in a Needs improvement performance was noted. From 24 PT cycles, the performance with Excellent, Good, Fair, and Needs improvement was ranging from 10.5%-95.8%, 0%-11.3%, 0%-77.2%, and 2.3%-37.0%, respectively.

CONCLUSION

Most participants have proven their performance to be reliable and demonstrated their abilities to provide interpretation and genetic risk assessment on most of the PT items. For complex thalassemia however, a need to improve the interpretation and risk assessment skills is required which is essential for effective prevention and control of severe thalassemia diseases in Thailand.

β-thalassemia minor is a beneficial determinant of red blood cell storage lesion

Blood donor genetics and lifestyle affect the quality of red blood cell (RBC) storage. Heterozygotes for beta thalassemia (bThal⁺) constitute a non-negligible proportion of blood donors in the Mediterranean and other geographical areas. The unique hematological profile of bThal⁺ could affect the capacity of enduring storage stress, however, the storability of bThal⁺ RBC is largely unknown. In this study, RBC from 18 bThal⁺ donors were stored in the cold and profiled for primary (hemolysis) and secondary (phosphatidylserine exposure, potassium leakage, oxidative stress) quality measures, and metabolomics, versus sex- and age-matched controls. The bThal⁺ units exhibited better levels of storage hemolysis and susceptibility to lysis following osmotic, oxidative and mechanical insults. Moreover, bThal⁺ RBC had a lower percentage of surface removal signaling, reactive oxygen species and oxidative defects to membrane components at late stages of storage. Lower potassium accumulation and higher uratedependent antioxidant capacity were noted in the bThal⁺ supernatant. Full metabolomics analyses revealed alterations in purine and arginine pathways at baseline, along with activation of the pentose phosphate pathway and glycolysis upstream to pyruvate kinase in bThal⁺ RBC. Upon storage, substantial changes were observed in arginine, purine and vitamin B6 metabolism, as well as in the hexosamine pathway. A high degree of glutamate generation in bThal⁺ RBC was accompanied by low levels of purine oxidation products (IMP, hypoxanthine, allantoin). The bThal mutations impact the metabolism and the susceptibility to hemolysis of stored RBC, suggesting good post-transfusion recovery. However, hemoglobin increment and other clinical outcomes of bThal⁺ RBC transfusion deserve elucidation by future studies.

Laboratory approach to investigation of anemia with a focus on pyruvate kinase deficiency

Anemia is a major health burden worldwide and affects approximately one-third of world's population. It is not a diagnosis; it is a manifestation of an underlying pathophysiology leading to either decreased hemoglobin (Hb), hematocrit (Hct), or red blood cells (RBCs). Iron deficiency anemia is still the most common cause of anemia worldwide. The symptoms are usually due to the underlying compensatory responses to decrease in oxygen delivery to the tissues. Laboratory investigation should start with complete blood count (CBC), reticulocyte count (RC), and peripheral smear evaluation. Further testing depends on these indices, that is, iron parameters and hemoglobinopathies/thalassemia evaluation in microcytic hypochromic anemia, vitamin B12, and folic acid level in macrocytic anemia. Increased RC denotes adequate bone marrow response and points toward hemolytic process and vice versa. Anemia diagnosis can be complex and confusing for the practicing physician. This review tries to give a practical simplistic approach to the diagnosis, focusing mainly on the basic parameters, that is, CBC, RC, and peripheral smear etc. Moreover, we have also tried to provide an update on the pyruvate kinase deficiency, as there has been recent exciting development in the management of these patients.

A "One-Stop" Screening Protocol for Haemoglobinopathy Traits and Iron Deficiency in Sri Lanka

Introduction: The high frequencies of carriers of severe haemoglobinopathies and of iron deficiency in Southeast Asia require reliable and affordable tests to improve on current screening procedures. Objectives: We evaluate a "one stop" approach using the THALCON dichlorophenolindophenol (DCIP) and one-tube osmotic fragility (OF) tests and measurement of Zinc Protoporphyrin (ZPP) to detect and distinguish HbE and β-thalassaemia traits from iron deficiency. We compare findings with current screening practice in Sri Lanka that relies on the identification of low mean red cell volume and/or mean red cell hemoglobin for this purpose. Methods: Between November 2017 and May 2018, we undertook a cross-sectional survey of secondary school students in Gampaha district, Sri Lanka. The THALCON-DCIP and OF tests were compared to capillary electrophoresis (CE), used as a gold standard to detect haemoglobinopathies. ZPP was measured in whole blood. Plasma ferritin and C-reactive protein (CRP) were measured in students with a raised ZPP concentration. Results: We collected venous blood samples from 1,324/1,332 (99.4%) students. The median age of the students was 17 (IQR 16-18) years, all were Sinhalese and 814/1,324 (61.5%) were female. CE identified 3 students with HbE trait and 26 students with β-thalassaemia trait. The THALCON-DCIP test was positive only in the 3 students with HbE (sensitivity 100%, 95% CI 29.2-100.0; specificity 100%, 95% CI 99.7-100.0). The THALCON-OF test identified all 26 students with β-thalassaemia trait (sensitivity = 100%, 95% CI 86.8-100.0) and 287 students with a normal CE result (specificity = 77.9%; 95% CI 75.5-80.1). It was also positive in 2/3 (66.7%) students with HbE trait. Iron deficiency (ZPP > 70 μmol/mol heme) was present in 118/1,240 (9.5%) students with a normal hemoglobin genotype, all of whom had plasma ferritin <15 ng/ml and CRP <5 mg/L. Conclusion: This one-stop approach offers reliable and affordable population screening for both haemoglobinopathy traits and iron deficiency in resource-limited settings where these conditions are common and ensures that iron supplements are targeted only to those who require them. Further work is warranted to refine the OF test to reduce the number of false positive results.