On the feasibility of malaria hypothesis.

In 1954, Allison proposed that hemoglobin S (HbS) gene causes protection against fatal malaria. This would explain the high HbS gene frequency observed in certain regions hyperendemic for malaria, so-called "malaria hypothesis". This in silico study was conducted to examine the feasibility of the hypothesis under more realistic initial conditions, where a mutant gene with heterozygous advantage against malaria (e.g., HbS) was introduced in a group of Neolithic hunter-gatherers who decided to start agriculture nearby water where malaria killed a proportion of population. The tribe population size, number of children born to each woman in each generation, mortality from malaria and sickle cell disease, the protection factor provided by the gene carriers against malaria, the probability of mating between the members of the parent and offspring populations, population growth, and increased fertility in women heterozygous for HbS, were also considered. For effectively confer protection against malaria within the shortest possible period, the mutation needs to be happened in a small population. For a large population, the process would take around 100 generations (~ 2500 years) or more to provide an effective protection. Even then, the probability that the new gene could survive and propagate to future generations is about 35%. Conventional population genetics equations with differential or difference equations, give totally incorrect estimates of the gene frequency in small populations; discrete mathematics should be used, instead. After introduction of the advantageous mutation, the gene frequency increased until a steady state value. This value is far less than the gene frequency reported in certain tribes of Africa. It seems that the malaria hypothesis, per se, could not explain such a high observed gene frequency, unless HbS is associated with lower mortality from other causes too.

Evaluating sheep hemoglobins with MD simulations as an animal model for sickle cell disease.

Sickle cell disease (SCD) affects millions worldwide, yet there are few therapeutic options. To develop effective treatments, preclinical models that recapitulate human physiology and SCD pathophysiology are needed. SCD arises from a single Glu-to-Val substitution at position 6 in the ß subunit of hemoglobin (Hb), promoting Hb polymerization and subsequent disease. Sheep share important physiological and developmental characteristics with humans, including the same developmental pattern of fetal to adult Hb switching. Herein, we investigated whether introducing the SCD mutation into the sheep ß-globin locus would recapitulate SCD's complex pathophysiology by generating high quality SWISS-MODEL sheep Hb structures and performing MD simulations of normal/sickle human (huHbA/huHbS) and sheep (shHbB/shHbS) Hb, establishing how accurately shHbS mimics huHbS behavior. shHbS, like huHbS, remained stable with low RMSD, while huHbA and shHbB had higher and fluctuating RMSD. shHbB and shHbS also behaved identically to huHbA and huHbS with respect to ß2-Glu6 and ß1-Asp73 (ß1-Asn72 in sheep) solvent interactions. These data demonstrate that introducing the single SCD-causing Glu-to-Val substitution into sheep ß-globin causes alterations consistent with the Hb polymerization that drives RBC sickling, supporting the development of a SCD sheep model to pave the way for alternative cures for this debilitating, globally impactful disease.

Bach1 inhibitor HPP-D mediates γ-globin gene activation in sickle erythroid progenitors.

Sickle cell disease (SCD) is the most common ß-hemoglobinopathy caused by various mutations in the adult ß-globin gene resulting in sickle hemoglobin production, chronic hemolytic anemia, pain, and progressive organ damage. The best therapeutic strategies to manage the clinical symptoms of SCD is the induction of fetal hemoglobin (HbF) using chemical agents. At present, among the Food and Drug Administration-approved drugs to treat SCD, hydroxyurea is the only one proven to induce HbF protein synthesis, however, it is not effective in all people. Therefore, we evaluated the ability of the novel Bach1 inhibitor, HPP-D to induce HbF in KU812 cells and primary sickle erythroid progenitors. HPP-D increased HbF and decreased Bach1 protein levels in both cell types. Furthermore, chromatin immunoprecipitation assay showed reduced Bach1 and increased NRF2 binding to the γ-globin promoter antioxidant response elements. We also observed increased levels of the active histone marks H3K4Me1 and H3K4Me3 supporting an open chromatin configuration. In primary sickle erythroid progenitors, HPP-D increased γ-globin transcription and HbF positive cells and reduced sickled erythroid progenitors under hypoxia conditions. Collectively, our data demonstrate that HPP-D induces γ-globin gene transcription through Bach1 inhibition and enhanced NRF2 binding in the γ-globin promoter antioxidant response elements.

Calcium flux alterations in erythrocytes from sickle cell mice: The relevance of mean corpuscular volume.

Red blood cells (RBC) from patients with sickle cell disease (SCD) have elevated calcium levels at baseline, which are further elevated upon deoxygenation. Here we examined baseline calcium levels and calcium flux in RBCs from a mouse model of SCD mice. We found that akin to humans with SCD, sickle (HbSS) Townes mice, have higher baseline levels and increased calcium flux in RBCs compared to control (HbAA) animals. As HbSS mice, unlike humans with SCD, have high mean corpuscular volume compared with HbAA, we highlight the importance of adjusting biochemical results to number of RBCs rather than hematocrit during the analysis and interpretation of the results. Our findings add to the face validity of humanized sickle cell mice and support its use for studies of RBC calcium flux in SCD.

An α-chain modification rivals the effect of fetal hemoglobin in retarding the rate of sickle cell fiber formation.

Adults with sickle cell disease bear a mutation in the ß-globin gene, leading to the expression of sickle hemoglobin (HbS; α2ßS2). Adults also possess the gene for γ-globin, which is a component of fetal hemoglobin (HbF, α2γ2); however, γ-chain expression normally ceases after birth. As HbF does not form the fibers that cause the disease, pharmacological and gene-modifying interventions have attempted to either reactivate expression of the γ chain or introduce a gene encoding a modified ß chain having γ-like character. Here, we show that a single-site modification on the α chain, αPro114Arg, retards fiber formation as effectively as HbF. Because this addition to the repertoire of anti-sickling approaches acts independently of other modifications, it could be coupled with other therapies to significantly enhance their effectiveness.

High Throughput Newborn Screening for Sickle Cell Disease - Application of Two-Tiered Testing with a qPCR-Based Primary screen.

BACKGROUND: Sickle cell disease (SCD) is a group of hemoglobinopathies with a common point mutation causing the production of sickle cell hemoglobin (HbS). In high-throughput newborn screening (NBS) for SCD, a two-step procedure is suitable, in which qPCR first pre-selects relevant samples that are differentiated by a second method. METHODS: Three NBS centers using qPCR-based primary screening for SCD performed a laboratory comparison. Methods using tandem MS or HPLC were used for differentiation. RESULTS: In a benchmarking test, 450 dried blood samples were analyzed. Samples containing HbS were detected as reliably by qPCR as by methods established for hemoglobinopathy testing. In a two-step screening approach, the 2nd-tier-analyses have to distinguish the carrier status from pathological variants. In nine months of regular screening, a total of 353,219 samples were analyzed using two-stage NBS procedures. The 1st-tier screening by qPCR reduced the number of samples for subsequent differentiation by>99.5%. Cases with carrier status or other variants were identified as inconspicuous while 78 cases with SCD were revealed. The derived incidence of 1:4,773, is in good agreement with previously published incidences. CONCLUSION: In high-throughput NBS for SCD, qPCR is suitable to focus 2nd-tier analyses on samples containing HbS, while being unaffected by factors such as prematurity or transfusions. The substantial reduction of samples numbers positively impacts resource conservation, sustainability, and cost-effectiveness. No false negative cases came to attention.

Demographics and outcomes of hemoglobin genotype in hospitalized patients with COVID-19 and sickle cell disease in the United States.

INTRODUCTION: Coronavirus disease 2019 (COVID-19) is associated with poor outcomes in sickle cell disease (SCD) patients. However, there is a paucity of data comparing hemoglobin (Hb) genotypes in SCD and infection outcomes. METHODS: The National Inpatient Sample was used to identify the record of hospitalizations with COVID-19 and SCD in 2020 using the International Classification of Disease, Tenth Revision codes. Study outcomes (invasive mechanical ventilation, extracorporeal membrane oxygenation, shock, vasopressor use, measures of resource utilization, and in-hospital mortality) were compared between hemoglobin SS, SC, and S-beta thalassemia (Sß). RESULTS: Of the 102 975 COVID-19 hospitalizations with SCD, 87.26% had HbSS, 7.16% had HbSC, and 5.58% had HbSß. Younger patients were more likely to have HbSS, while older patients were likely to have HbSC and HbSß. HbSS was more frequent with Blacks, while HbSß was more prevalent with Whites and Hispanics. Though measures of resource utilization were higher in HbSS, there was no significant difference in in-hospital outcomes between the three genotypes. CONCLUSION: There is no difference in COVID-19 outcomes among Hb genotypes in SCD. Further studies are needed to explore the reasons for this observation.

Effect of α+ Thalassemia on the Severity of Plasmodium falciparum Malaria in Different Sickle Cell Genotypes in Indian Adults: A Hospital-Based Study.

There is a paucity of literature on the association of α+-thalassemia, sickle-cell hemoglobin disorders, and malaria in India. This study aimed to understand the effect of α+-thalassemia on the severity of Plasmodium falciparum malaria in adults with respect to sickle-cell genotypes. The study subjects were categorized into 'severe-malaria' and 'uncomplicated-malaria' and age-gender matched 'control' groups. Sickle-cell and α+-thalassemia were investigated in all the recruited subjects. The effect of α+-thalassemia on the severity of malaria was analyzed in HbAA and sickle-cell genotypes (HbAS and HbSS) separately. The prevalence of α+-thalassemia in various groups ranged from 41.5% to 81.8%. The prevalence of α+-thalassemia was lower (OR = 1.64; p = 0.0013) in severe malaria (41.5%) as compared to healthy controls (53.8%) with HbAA genotype. In contrast, in HbAS genotype, the prevalence of α+-thalassemia was higher (OR = 4.11; p = 0.0002) in severe malaria (81.8%) compared to controls (52.2%). In severe malaria with HbAA genotype, there was a significantly higher hemoglobin level and low MCV and MCH level in patients with α+-thalassemia compared to the normal α-globin genotype. Further, the incidence of cerebral malaria, hepatopathy, and mortality was lower in patients (HbAA) with α+-thalassemia as compared to normal α-globin genotype (HbAA). In severe malaria with either HbAS or HbSS genotype, only a few parameters showed statistical differences with respect to α+-thalassemia. Low prevalence of α+-thalassemia in severe malaria with HbAA genotype compared to healthy controls with HbAA genotype indicates the protective effect of α+-thalassemia against severe malaria. However, the high prevalence of α+-thalassemia in patients with HbAS genotype depicts its interference in the protective effect of sickle-cell against severe malaria.

Newborn screening for sickle cell disease in Kisangani, Democratic Republic of the Congo: an update.

BACKGROUND: Neonatal screening is the first action necessary to identify children with sickle cell disease (SCD) and thus ensure their care. Using rapid tests to give an immediate result to families is a new resilient approach of great interest. These two aspects are essential for establishing an adequate health policy for this disease. This study was undertaken in Kisangani to update the current incidence of neonatal SCD. METHODS: Heel prick blood samples of 1432 babies born from different racial groups of parents living in Kisangani were collected at birth and screened using a point of care test, i.e. the HemoTypeSCTM. RESULTS: The incidence at birth was 2.2% (n = 31; 95% CI: [1.5%-3.1%]) for HbSS homozygosity and 21% (n = 303; 95% CI: [19%-23%]) for HbAS heterozygosity. Compared to a previous study in 2010; the incidence at the birth of the HbSS form has doubled, while that of the heterozygous form HbAS remained almost unchanged. The inter-ethnic incidence of HbSS among the five top-represented ethnic groups was significant (<0.001). CONCLUSION: The prevalence of homozygote form has doubled compared to the 0.96% reported in 2010. Setting up a neonatal screening program and an awareness unit is necessary to assess the need for care services correctly.

Sickle Cell Hemoglobin Genotypes Affect Malaria Parasite Growth and Correlate with Exosomal miR-451a and let-7i-5p Levels.

Malaria affects a significant portion of the global population, with 247 million cases in 2021, primarily in Africa. However, certain hemoglobinopathies, such as sickle cell trait (SCT), have been linked to lower mortality rates in malaria patients. Hemoglobin (Hb) mutations, including HbS and HbC, can cause sickle cell disease (SCD) when both alleles are inherited (HbSS and HbSC). In SCT, one allele is inherited and paired with a normal allele (HbAS, HbAC). The high prevalence of these alleles in Africa may be attributed to their protective effect against malaria. Biomarkers are crucial for SCD and malaria diagnosis and prognosis. Studies indicate that miRNAs, specifically miR-451a and let-7i-5p, are differentially expressed in HbSS and HbAS compared to controls. Our research examined the levels of exosomal miR-451a and let-7i-5p in red blood cells (RBCs) and infected red blood cells (iRBCs) from multiple sickle Hb genotypes and their impact on parasite growth. We assessed exosomal miR-451a and let-7i-5p levels in vitro in RBC and iRBC supernatants. Exosomal miRNAs exhibited distinct expression patterns in iRBCs from individuals with different sickle Hb genotypes. Additionally, we discovered a correlation between let-7i-5p levels and trophozoite count. Exosomal miR-451a and let-7i-5p could modulate SCD and malaria severity and serve as potential biomarkers for malaria vaccines and therapies.

Reticulocyte mitochondrial retention increases reactive oxygen species and oxygen consumption in mouse models of sickle cell disease and phlebotomy-induced anemia.

Sickle cell disease (SCD) is caused by a mutation of the ß-globin gene that results in the production of hemoglobin S (HbS). People with SCD experience anemia, severe acute pain episodes, persistent chronic pain, multiorgan damage, and a reduced life span. The pathophysiology of SCD caused by the polymerization of HbS on deoxygenation results in red cell deformability and the generation of reactive oxygen species (ROS). These 2 factors lead to red cell fragility and hemolysis. Reticulocytosis is an independent predictor of disease morbidity and mortality in SCD. We previously established that humans and mice with SCD exhibit abnormal mitochondrial retention in erythrocytes increasing ROS-associated hemolysis. Here, we investigated the hypothesis that mitochondrial retention and increased ROS are a consequence of stress erythropoiesis. Our results show clearly that stress erythropoiesis in phlebotomized, anemic AA mice results in mitochondrial retention and increased ROS in reticulocytes. We observed that elevated mitochondrial retention in reticulocytes also alters oxygen consumption and potentially contributes to increased HbS polymerization and red blood cell hemolysis. Therefore, these events occurring due to stress erythropoiesis contribute significantly to the pathology of SCD and suggest new therapeutic targets.

The Sickle-Cell Fiber Revisited.

Sickle cell disease is the consequence of a single point mutation on the surface of the ß chains of the hemoglobin molecule leading to the formation of rigid polymers that disrupt circulation. It has long been established that the polymers are comprised of seven pairs of double strands that are twisted replicas of the double strands found in crystals. Here, we review several newer developments that elaborate on that simple model and provide deeper insights into the process.

Most adults with severe HbSC disease are not treated with hydroxyurea.

Sickle cell hemoglobin SC (HbSC) disease is the second most frequent sickle cell disease (SCD) genotype after sickle cell anemia (HbSS). Globally, ∼55 000 newborns with HbSC are delivered annually, with the highest HbC gene frequency in West Africa. In Ghana, 40% of adults visiting the Ghana Institute of Clinical Genetics SCD clinic have HbSC. Unlike HbSS, hydroxyurea use is not routinely recommended for individuals with HbSC because of the perceived high-risk to benefit ratio. To test the hypothesis that at least 5% of adults with HbSC will meet the American Society of Hematology criteria for severe disease, we conducted a retrospective descriptive cohort study of all individuals with HbSC (≥18 years) who visited the clinic in 2019. Adults with HbSC aged from 18 to 45 years were selected. We identified a comparison group of 639 individuals with HbSS and matched the frequency based on the age and sex of individuals with HbSC. Severe disease was defined as a history of ≥3 SCD-associated moderate or severe pain episodes per year, history of acute chest syndrome, and severe symptomatic chronic anemia that interferes with daily activities or quality of life. The study end points were the proportion of individuals with SCD who met the definition of severe disease and were eligible for hydroxyurea. In total, 64 of 639 (10.0%) individuals with HbSC met the eligibility criteria for hydroxyurea therapy compared with 154 of 639 (24.1%) individuals with HbSS. Less than 1% and 3% of individuals with severe HbSC and HbSS, respectively, were routinely prescribed with hydroxyurea in this tertiary care medical center.

In vivo HSC prime editing rescues sickle cell disease in a mouse model.

Sickle cell disease (SCD) is a monogenic disease caused by a nucleotide mutation in the ß-globin gene. Current gene therapy studies are mainly focused on lentiviral vector-mediated gene addition or CRISPR/Cas9-mediated fetal globin reactivation, leaving the root cause unfixed. We developed a vectorized prime editing system that can directly repair the SCD mutation in hematopoietic stem cells (HSCs) in vivo in a SCD mouse model (CD46/Townes mice). Our approach involved a single intravenous injection of a nonintegrating, prime editor-expressing viral vector into mobilized CD46/Townes mice and low-dose drug selection in vivo. This procedure resulted in the correction of ∼40% of ßS alleles in HSCs. On average, 43% of sickle hemoglobin was replaced by adult hemoglobin, thereby greatly mitigating the SCD phenotypes. Transplantation in secondary recipients demonstrated that long-term repopulating HSCs were edited. Highly efficient target site editing was achieved with minimal generation of insertions and deletions and no detectable off-target editing. Because of its simplicity and portability, our in vivo prime editing approach has the potential for application in resource-poor countries where SCD is prevalent.

Ancestral reconstruction and correlation of the frequencies of the hemoglobin S allele and the Duffy blood group alleles in human populations.

OBJECTIVES: Malaria is an important selective force for human genetic adaptation due to the sustained, lethal impact it has had on populations worldwide. High frequencies of both hemoglobin S and the null allele FYBES of the Duffy blood group have been found in areas where this disease is endemic, attributed to the protective action of the carriers of these variants against malaria infection. The objective of this work was to perform ancestral reconstruction and analyze the correlation of the frequencies of these alleles throughout the phylogeny of 24 human populations. METHODS: A tree topology and the allelic frequencies reported in the literature for the 24 populations were used. The ancestral frequencies for the two alleles were reconstructed using the maximum likelihood method and the Brownian model of evolution (CI = 95%), and the correlation analysis was performed using phylogenetically independent contrasts (PICs). Statistical analyses were performed with the statistical software R version 3.4.1. RESULTS: For both alleles, a correspondence was found in the reconstruction of the ancestral frequencies, and a significant statistical correlation (p = .001) was observed between the S and FYBES alleles. CONCLUSIONS: These results provide evidence of an epistatic relationship between the two alleles, which may influence the fitness of the individuals who present with them when they are subjected to a selective force such as malaria.

Knowledge and DdeI Based Confirmation of Sickle Cell Anemia Among the Tharu Community.

BACKGROUND: Sickle cell anemia is an inherited blood disorder caused due to a point mutation at the sixth codon of the ?-globin gene of both alleles. Sickle cell traits occur when the mutation is in one of the two alleles of the ?-globin genes. This study was carried out in the Tharu community, which is an indigenous and minority group mostly residing in the Terai region of Nepal. They are also considered as the most vulnerable group for inheriting Sickle cell anemia. METHODS: Purposive sampling, which included 130 Tharu individuals of Kanchanpur district of Nepal, was considered for the study. The survey was conducted using a descriptive questionnaire that contained relevant information including the family history of Sickle cell anemia. This was followed by the analysis of blood samples to determine the prevalence of Sickle cell anemia and Sickle cell traits. Primer-mediated enzymatic amplification of target sequences in genomic DNA followed by restriction endonuclease assay with an enzyme DdeI was carried out for the confirmation. RESULTS: Among 130 individuals, only 55.4% had basic knowledge about Sickle cell anemia. After screening for sickle cell anemia from 60 participants, 27 (45%) of them were found to be in the heterozygous state (carrier, Hb AS) and 28 (46.7%) were in the homozygous (normal, AA Hb) state with 5 (8.3%) having the diseased hemoglobin (Hb SS) variant of Sickle cell anemia. CONCLUSIONS: This study demonstrated a high prevalence of Sickle cell anemia and Sickle cell traits in the Tharu community. This study may be beneficial for concerned personnel policymakers to reduce sickle cell cases by improving genetic literacy among the Tharu community.

Epigenetic analysis in placentas from sickle cell disease patients reveals a hypermethylation profile.

Pregnancy in Sickle Cell Disease (SCD) women is associated to increased risk of clinical and obstetrical complications. Placentas from SCD pregnancies can present increased abnormal findings, which may lead to placental insufficiency, favoring adverse perinatal outcome. These placental abnormalities are well known and reported, however little is known about the molecular mechanisms, such as epigenetics. Thus, our aim was to evaluate the DNA methylation profile in placentas from women with SCD (HbSS and HbSC genotypes), compared to uncomplicated controls (HbAA). We included in this study 11 pregnant women with HbSS, 11 with HbSC and 21 with HbAA genotypes. Illumina Methylation EPIC BeadChip was used to assess the whole placental DNA methylation. Pyrosequencing was used for array data validation and qRT-PCR was applied for gene expression analysis. Our results showed high frequency of hypermethylated CpGs sites in HbSS and HbSC groups with 73.5% and 76.2% respectively, when compared with the control group. Differentially methylated regions (DMRs) also showed an increased hypermethylation status for the HbSS (89%) and HbSC (86%) groups, when compared with the control group methylation data. DMRs were selected for methylation validation (4 DMRs-HbSS and 3 DMRs the HbSC groups) and after analyses three were validated in the HbSS group, and none in the HbSC group. The gene expression analysis showed differential expression for the PTGFR (-2.97-fold) and GPR56 (3.0-fold) genes in the HbSS group, and for the SPOCK1 (-2.40-fold) and ADCY4 (1.80-fold) genes in the HbSC group. Taken together, these data strongly suggest that SCD (HbSS and HbSC genotypes) can alter placental DNA methylation and lead to gene expression changes. These changes possibly contribute to abnormal placental development and could impact in the clinical course, especially for the fetus, possibly leading to increased risk of abortion, fetal growth restriction (FGR), stillbirth, small for gestational age newborns and prematurity.

Fetal hemoglobin regulating genetic variants identified in homozygous (HbSS) and heterozygous (HbSA) subjects from South Mexico.

Hemoglobin S is caused by a nucleotide change in HBB gene (HBB:c.20A>T, p.Glu6Val), is presented in diverse forms: simple carriers (HbSA), homozygotes (HbSS) also known as sickle cell anemia, and compound heterozygotes with other ß-hemoglobinopathies. It is worldwide distributed, in Mexico, is frequently observed in the southern states Guerrero, Oaxaca and Chiapas. Elevated fetal hemoglobin (HbF) is associated with mild phenotype; single-nucleotide variants (SNVs) in modifier genes, such as BCL11A, HBG2, HBBP1 pseudogene and HBS1L-MYB intergenic region, upregulate HbF synthesis. The aim of this study was to identify HbF regulating genetic variants in HbSS and HbSA Mexican subjects. We studied 39 individuals (HbSS = 24, 61%, HbSA = 15, 39%) from Chiapas (67%) and Guerrero (33%), peripheral blood was collected in ethylenediamine tetraacetic acid (EDTA) for molecular and hematological studies, DNA was isolated by salting-out technic and genotyping was performed through allelic discrimination by real time polymerase chain reaction (RT-PCR) using Taqman® probes for 15 SNV (in BCL11A: rs6706648, rs7557939, rs4671393, rs11886868, rs766432, rs7599488, rs1427407; HBS1L-MYB: rs28384513, rs7776054, rs9399137, rs4895441, rs9402686, rs1320963; HBG2: rs7482144; and HBBP1: rs10128556). The obtained data were analyzed using IMB SPSS v.22.0 software. All minor alleles were observed in frequencies over 0.05, the most frequent was rs9402686 (0.82), while the less frequent was rs101028556 (0.08). In HbSS group, the mean fetal hemoglobin was 11.9 ± 5.9% and was significantly elevated in BCL11A rs11886868 wildtype homozygotes and in carriers of HBS1L-MYB intergenic region rs7776054 (p = 0.04 and p = 0.03, respectively). In conclusion, in HbSS Mexican patients, two SNVs were observed related to increased HbF; BCL11A rs11886868 and HBS1L-MYB rs7776054.

Sickle cell anemia (SCA) is one of the most common types of hemoglobinopathies in people of African ancestry, it is caused by homozygosity of HbS mutation (HBB:c.20A>T). It is known that fetal hemoglobin plays a key role in decreasing HbS polymerization which damages the erythrocyte structure and is responsible for the characteristic hemolytic crises endured by these patients. Single-nucleotide variant (SNV) in genes that regulate fetal hemoglobin (HbF) after birth have been associated with its increment, thus ameliorating the hematologic phenotype of this pathology and other ß-hemoglobinopathies. Therefore, in this study, we identified, for the first time in Mexican patients with SCA (HbSS) and HbS carriers (HbSA), the presence of 15 SNVs on BCL11A, HBS1L-MYB and HBG2; all HbSS patients had anemia and elevated HbF; 2 variants were related to increased HbF rs11688888C of BCL11A and rs7776054G of HBSIL-MYB; and finally, all minor alleles were found at a frequency higher than 0.05.

Newborn screening for abnormal haemoglobins in Jamaica: Practical issues in an island programme.

OBJECTIVE: To report the diagnostic challenges of newborn screening for abnormal haemoglobins. SETTING: Cord blood samples from 13 hospitals in southwest Jamaica taken in 2008-2019. METHODS: Blood spots, collected from the umbilical cord, were analysed by high pressure liquid chromatography (HPLC) to reveal phenotypes for HbSS and HbCC, but genotype confirmation may require parental studies or gene sequencing. Such cases that were successfully traced were analysed in this follow-up study. RESULTS: HPLC screening of 121,306 samples detected HbAS in 11,846 (9.8%), HbAC in 4508 (3.7%) and other electrophoretic abnormalities in 1090 babies. Among 101 previously unconfirmed cases, 34/90 (38%) with HPLC evidence of a HbSS phenotype had other genotypes, and 7/11 (64%) with a HbCC phenotype had other genotypes. Syndromes from the interaction of ß thalassaemia occurred in 112 babies (85 with HbS, 27 with HbC) and of genes for hereditary persistence of fetal haemoglobin (HPFH) in 18 (12 with HbS, 6 with HbC). Variants other than HbS and HbC occurred in 270 babies, 16 in combination with either HbS or HbC, and 254 as traits. Most variants are benign even when inherited with HbS, although HbO Arab, HbD Punjab, or Hb Lepore Washington, which occurred in 6 cases, may cause sickle cell disease. CONCLUSIONS: Genes for ß thalassaemia and HPFH are common in western Jamaica and when associated with HbS may present diagnostic challenges in newborns, as HbF and HbA2 have not reached diagnostic levels. Family and DNA studies may be necessary for genotype confirmation.