A comparative study of hematological parameters of α and β thalassemias in a high prevalence zone: Saudi Arabia

Phenotypic Variability and Hematological Characterization of β0- and β+-Thalassemia Carriers: A Comparative Study

Background

β-Thalassemia is a genetic disorder characterized by decreased or completely absent β-globin synthesis, leading to a spectrum of clinical manifestations. It is a major public health concern in Jordan, as in other Mediterranean countries. β-Thalassemia carriers are normally asymptomatic; nevertheless, laboratory examinations often reveal mild anemia characterized by microcytic hypochromic erythrocytes, with differences influenced by specific phenotypes. This study aimed to assess and correlate the variants among β0 and β+ phenotypes in the Jordanian population with hematological characteristics, as well as establish and determine reference values for distinguishing between the two phenotypes.

Methods

One hundred forty-five β-thalassemia carriers were recruited from various governorates in Jordan. Hematological parameters, including complete blood count (CBC) and capillary electrophoresis of hemoglobin (Hb), were evaluated in all participants. Molecular techniques, specifically polymerase chain reaction (PCR) with hybridization, were employed to identify β-thalassemia variants and classify the participants as having β0 and β+ phenotypes.

Results

Among the 145 β-thalassemia carriers, 64 (44.14%) and 81 (55.86%) had β0-thalassemia and β+-thalassemia, respectively. Participants exhibiting a cutoff value of Hb (≤ 11.0 g/dL), mean corpuscular volume (MCV) (≤ 64.0 fL), mean corpuscular hemoglobin (MCH) (≤ 19.0 pg), and hemoglobin A2 (Hb-A2) (≥ 5.00%) were classified as having the β0 phenotype. These participants demonstrated significantly lower mean Hb, MCV, MCH, and higher mean Hb-A2 than the participants with the β+ phenotype (P < 0.0001).

Conclusions

Hb, MCV, MCH, and Hb-A2 can serve as effective screening tools for predicting β0- and β+-thalassemia in the Jordanian population. These findings have important clinical implications for early diagnosis, genetic counseling, and prenatal screening of β-thalassemia.

A Novel Algorithm Using Cell Population Data (VCS Parameters) as a Screening Discriminant between Alpha and Beta Thalassemia Traits

Thalassemia is one of the major inherited haematological disorders in the Southeast Asia region. This study explored the potential utility of red blood cell (RBC) parameters and reticulocyte cell population data (CPD) parameters in the differential diagnosis of α and β-thalassaemia traits as a rapid and cost-effective tool for screening of thalassemia traits. In this study, a total of 1597 subjects (1394 apparently healthy subjects, 155 subjects with α-thalassaemia trait, and 48 subjects with β-thalassaemia trait) were accrued. The parameters studied were the RBC parameters and reticulocyte CPD parameters derived from Unicel DxH800. A novel algorithm named αβ-algorithm was developed: (MN-LMALS-RET × RDW) − MCH) to discriminate α from β-thalassaemia trait with a cut-off value of 1742.5 [AUC = 0.966, sensitivity = 92%, specificity = 90%, 95% CI = 0.94–0.99]. Two prospective studies were carried: an in-house cohort to assess the specificity of this algorithm in 310 samples comprising various RBC disorders and in an interlaboratory cohort of 65 α-thalassemia trait, and 30 β-thalassaemia trait subjects to assess the reproducibility of the findings. We propose the αβ-algorithm to serve as a rapid, inexpensive surrogate evaluation tool of α and β-thalassaemia in the population screening of thalassemia traits in geographic regions with a high burden of these inherited blood disorders.

Thalassemia, a human blood disorder

A group of inherited blood defects is known as Thalassemia is among the world's most prevalent hemoglobinopathies. Thalassemias are of two types such as Alpha and Beta Thalassemia. The cause of these defects is gene mutations leading to low levels and/or malfunctioning α and β globin proteins, respectively. In some cases, one of these proteins may be completely absent. α and β globin chains form a globin fold or pocket for heme (Fe++) attachment to carry oxygen. Genes for alpha and beta-globin proteins are present in the form of a cluster on chromosome 16 and 11, respectively. Different globin genes are used at different stages in the life course. During embryonic and fetal developmental stages, γ globin proteins partner with α globin and are later replaced by β globin protein. Globin chain imbalances result in hemolysis and impede erythropoiesis. Individuals showing mild symptoms include carriers of alpha thalassemia or the people bearing alpha or beta-thalassemia trait. Alpha thalassemia causes conditions like hemolytic anemia or fatal hydrops fetalis depending upon the severity of the disease. Beta thalassemia major results in hemolytic anemia, growth retardation, and skeletal aberrations in early childhood. Children affected by this disorder need regular blood transfusions throughout their lives. Patients that depend on blood transfusion usually develop iron overload that causes other complications in the body systems like renal or hepatic impairment therefore, thalassemias are now categorized as a syndrome. The only cure for Thalassemias would be a bone marrow transplant, or gene therapy with currently no significant success rate. A thorough understanding of the molecular basis of this syndrome may provide novel insights and ideas for its treatment, as scientists have still been unable to find a permanent cure for this deadly disease after more than 87 years since it is first described in 1925.

Effects of -3.7α Deletion and Sickle-Cell Trait on Ventilatory and Hemodynamic Responses to Maximum Exercise in Young Saudi Females

Introduction

Hemoglobinopathies are common disorders in Saudi Arabia and have an impact on the general health of the affected individuals. The current study aimed to find out the effects of the presence of α 3.7 kb rightward deletion or sickle-cell trait (SCT) on ventilatory and hemodynamic parameters of maximum exercise testing in young Saudi women.

Methods

In a cross-sectional study, 75 randomly selected female students from different colleges were tested for VO_2max using a COSMED system for maximum exercise testing. Blood parameters and globin genotyping were determined.

Results

Hemoglobin genetic studies revealed 28 of the students had 3.7 α-globin deletion only (^−3.7α₂/α₁α₂), five had SCT, and 42 had normal α-globin (α₁α₂/α₁α₂ and no HbS) and were considered the control group. Subjects with ^−3.7α₂/α₁α₂ showed significantly lower VO_2max and higher resting systolic blood pressure, while SCT carriers showed no difference in regard to ventilatory parameters, but had higher post-exercise systolic blood pressure than controls.

Conclusion

It is concluded that individuals with 3.7 α-globin deletion might have lower fitness capacity, as demonstrated by lower VO_2max, which might explain the general lower VO_2max in the young women of this population. Furthermore, increments in resting systolic and posteexercise systolic blood pressure in 3.7 α-globin deletion and SCT, respectively, might indicate a future risk of cardiovascular diseases and require attention and extensive studies.

Distribution of hemoglobinopathy disorders in Saudi Arabia based on data from the premarital screening and genetic counseling program, 2011-2015

The prevalence rates of β-thalassemia (β-thal) and Sickle Cell Disease (SCD) in Saudi Arabia are considered one of the highest compared to surrounding countries in the Middle East (0.05% and 4.50%, respectively). In this study, Secondary data analysis was obtained from the premarital screening and genetic counseling program (PMSGC), and included 12,30,582 individuals from February 2011 to December 2015. Prevalence rates (per 1000 population) for β-thal and SCD were calculated for carrier status, disease status and their combination. During the 5-year study period, the overall prevalence rate per 1000 population for β-thal was 13.6 (12.9 for the trait and 0.7 for the disease). The prevalence rate for SCD was 49.6 (45.8 for the trait and 3.8 for the disease). Rates for β-thal were found to decrease from 24.2 in 2011, to 12 in 2015. However, SCD rates remained rather constant and ranged from 42.3 in 2011 to 49.8 in 2015. The highest rate for both β-thal and SCD was observed in the Eastern and Southern regions. This result reflects major accomplishment of the PMSGC. This study recommends further improvement in preventive measures in high-risk regions, and enhanced community awareness to provide the highest rate reduction for these disorders.

Molecular nature of alpha-globin genes in the Saudi population

Alpha-thalassemia (α-thal) is a disorder caused by the deletion of single or double α-globin genes, and/or point mutations in the α-globin genes. There are 2 common types of α-globin genes; HBA2 and HBA1. Recently, it has been discovered that the HBA2 gene is replaced by a unique HBA12 gene convert in 5.7% of the Saudi population. The α-globin genes have been emerging as a molecular target for the treatment of β-thalassemia (β-thal). Hence, it is essential to understand the molecular nature of α-globin genes to treat the most prevalent hemoglobin disorders, such as sickle cell disease, α-thal, and β-thal prevalent in the Kingdom of Saudi Arabia. Thirty-two different α-globin genotypes have been observed in the Saudi population. This review outlines the classification of the α-globin genes on the basis of their molecular nature and complex combinations of α-globin genes, and their variants predominant in Saudis.

Discrimination index of microcytic anemia in young soldiers: a single institutional analysis

Background

The common differential diagnosis of microcytic anemia in young Asian men includes iron deficiency anemia (IDA), α-thalassemia (αT) and β-thalassemia (βT). In this study, we aimed to distinguish between these diseases in a distinct population of young men using a specific index.

Patients and Methods

We retrospectively reviewed the laboratory data of young men with microcytic anemia. The clinical, characteristic and laboratory data, including complete blood cell counts, serum ferritin and hemoglobin electrophoresis results, were collected; genomic DNA mutations were also evaluated. Based on these data, ten discrimination indices were used to differentiate thalassemia from IDA. The sensitivity, specificity, positive and negative predictive values, Youden’s index and receiver operating characteristic (ROC) curves were also calculated.

Results

A total of 877 patients (92 patients with IDA, 332 with αT and 453 with βT) were enrolled; the Shine and Lal (S&L) formula was the best method with which to discriminate IDA from thalassemia (100% sensitivity, 91% specificity). The new cut-off values were evaluated, and the approaches used in our study cohort, particularly the Green & King (G&K) formula, significantly increased the accuracies of red cell distribution width-containing indices (cut-off value: 58.66; 89.62% sensitivity and 96.2% specificity; AUC: 0.9716). In addition, when applied properly, these indices could differentiate IDA patients from αT patients, especially Huber-Herklotz index (HH).

Conclusions

The sensitivity and specificity differed among ethnic and age groups. We concluded that when using the original cut-off value, the S&L formula was the best discriminating index for differentiating between IDA and thalassemia in young Asian men. However, when using the G&K formula, the newly obtained cut-off value must be applied to increase accuracy based on the results from our cohort.

Glucose-6-phosphate dehydrogenase deficiency among malaria suspects attending Gambella hospital, southwest Ethiopia

Background

Glucose-6-phosphate dehydrogenase deficiency (G6PDd) is widespread across malaria endemic regions. G6PD-deficient individuals are at risk of haemolysis when exposed, among other agents, to primaquine and tafenoquine, which are capable of blocking malaria transmission by killing Plasmodium falciparum gametocytes and preventing Plasmodium vivax relapses by targeting hypnozoites. It is evident that no measures are currently in place to ensure safe delivery of these drugs within the context of G6PDd risk. Thus, determining G6PDd prevalence in malarious areas would contribute towards avoiding possible complications in malaria elimination using the drugs. This study, therefore, was aimed at determining G6PDd prevalence in Gambella hospital, southwest Ethiopia, using CareStart™ G6PDd fluorescence spot test.

Methods

Venous blood samples were collected from febrile patients (n = 449) attending Gambella hospital in November-December 2013. Malaria was diagnosed using blood films and G6PDd was screened using CareStart™ G6PDd screening test (Access Bio, New Jersey, USA). Haematological parameters were also measured. The association of G6PD phenotype with sex, ethnic group and malaria smear positivity was tested.

Results

Malaria prevalence was 59.2% (96.6% of the cases being P. falciparum mono infections). Totally 33 participants (7.3%) were G6PD-deficient with no significant difference between the sexes. The chance of being G6PD-deficient was significantly higher for the native ethnic groups (Anuak and Nuer) compared to the ‘highlanders’/settlers (odds ratio (OD) = 3.9, 95% confidence interval (CI) 0.481-31.418 for Anuak vs ‘highlanders’; OD = 4.9, 95% CI 0.635-38.00 for Nuer vs ‘highlanders’). G6PDd prevalence among the Nuer (14.3%) was significantly higher than that for the Anuak (12.0%).

Conclusions

G6PDd prevalence in the area is substantial with 30 (90.9%) of the 33 deficient individuals having malaria suggesting the non-protective role of the disorder at least from clinical malaria. The indigenous Nilotic people tend to have a higher chance of being G6PD-deficient as 32 (96.9%) of the total 33 cases occurred among them.

Genome at juncture of early human migration: a systematic analysis of two whole genomes and thirteen exomes from Kuwaiti population subgroup of inferred Saudi Arabian tribe ancestry

Population of the State of Kuwait is composed of three genetic subgroups of inferred Persian, Saudi Arabian tribe and Bedouin ancestry. The Saudi Arabian tribe subgroup traces its origin to the Najd region of Saudi Arabia. By sequencing two whole genomes and thirteen exomes from this subgroup at high coverage (>40X), we identify 4,950,724 Single Nucleotide Polymorphisms (SNPs), 515,802 indels and 39,762 structural variations. Of the identified variants, 10,098 (8.3%) exomic SNPs, 139,923 (2.9%) non-exomic SNPs, 5,256 (54.3%) exomic indels, and 374,959 (74.08%) non-exomic indels are 'novel'. Up to 8,070 (79.9%) of the reported novel biallelic exomic SNPs are seen in low frequency (minor allele frequency <5%). We observe 5,462 known and 1,004 novel potentially deleterious nonsynonymous SNPs. Allele frequencies of common SNPs from the 15 exomes is significantly correlated with those from genotype data of a larger cohort of 48 individuals (Pearson correlation coefficient, 0.91; p <2.2×10-16). A set of 2,485 SNPs show significantly different allele frequencies when compared to populations from other continents. Two notable variants having risk alleles in high frequencies in this subgroup are: a nonsynonymous deleterious SNP (rs2108622 [19:g.15990431C>T] from CYP4F2 gene [MIM:*604426]) associated with warfarin dosage levels [MIM:#122700] required to elicit normal anticoagulant response; and a 3' UTR SNP (rs6151429 [22:g.51063477T>C]) from ARSA gene [MIM:*607574]) associated with Metachromatic Leukodystrophy [MIM:#250100]. Hemoglobin Riyadh variant (identified for the first time in a Saudi Arabian woman) is observed in the exome data. The mitochondrial haplogroup profiles of the 15 individuals are consistent with the haplogroup diversity seen in Saudi Arabian natives, who are believed to have received substantial gene flow from Africa and eastern provenance. We present the first genome resource imperative for designing future genetic studies in Saudi Arabian tribe subgroup. The full-length genome sequences and the identified variants are available at ftp://dgr.dasmaninstitute.org and http://dgr.dasmaninstitute.org/DGR/gb.html.

Half of the Emirati population has abnormal red cell parameters: challenges for standards and screening guidelines

In populations with high prevalences of iron deficiency and thalassemia trait, many apparently healthy individuals have abnormal erythroid parameters, which may cause diagnostic problems in clinical practice. We studied the prevalence and causes of red cell parameter values outside their reference ranges in 394 healthy individuals of Bedouin Arab origin, who had complete blood counts (CBCs), hemoglobin (Hb) analyses and serum ferritin tests done. Their mean age ± standard deviation (SD) was 24.8 ± 4.9 years and 51.8% were females. Overall, 53.0% (209/394) had low Hb, MCV or MCH or high RDW. Anemia was present in 27.0% (55/204) of the women and 3.0% (6/190) of the men. Overall prevalence of MCV < 80.0 fL was 45.0% (176/394) and MCH < 27.0 pg was 48.0% (190/394); RDW > 14.0% was found in 21.0% (43/204) of women and 7.0% (14/190) of men. Of the women, 16.0% had iron deficiency anemia (33/204) and 65.0% had ferritin values of < 30.0 μg/L (133/204). The estimated prevalence of α-thalassemia (α-thal) trait in men was 32.0% (60/190) and that of β-thalassemia (β-thal) trait in both sexes was 3.0% (12/394). In conclusion, half of the healthy Emirati population have abnormal CBC values. For clinical purposes, they require reference standards for red cells that are derived from their own population. Screening of women for iron deficiency is justified due to a high prevalence of iron deficiency.