Neonatal screening for hemoglobinopathies: results of a public health system in South Brazil

Systematic Literature Review Shows Gaps in Data on Global Prevalence and Birth Prevalence of Sickle Cell Disease and Sickle Cell Trait: Call for Action to Scale Up and Harmonize Data Collection

Sickle cell disease (SCD) is an inherited monogenic disorder with high prevalence throughout sub-Saharan Africa, the Mediterranean basin, the Middle East, and India. Sources of SCD epidemiology remain scarce and fragmented. A systematic literature review (SLR) to identify peer-reviewed studies on SCD epidemiology was performed, with a search of bibliographic databases and key conference proceedings from 1 January 2010 to 25 March 2022 (congress abstracts after 2018). The SLR followed PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Meta-analyses, using a binomial normal random-effects model, were performed to estimate global and regional prevalence and birth prevalence. Of 1770 journal articles and 468 abstracts screened, 115 publications met the inclusion criteria. Prevalence was highest in Africa (~800/100,000), followed by the Middle East (~200/100,000) and India (~100/100,000), in contrast to ~30/100,000 in Europe. Birth prevalence was highest in Africa (~1000/100,000) and lowest in North America (~50/100,000) and Europe (~30/100,000). This SLR confirmed that sub-Saharan and North-East Africa, India, the Middle East, and the Caribbean islands are global SCD hotspots. Publications including mortality data were sparse, and no conclusions could be drawn about mortality. The identified data were limited due to gaps in the published literature for large parts of the world population; the inconsistent reporting of SCD genotypes, diagnostic criteria, and settings; and a sparsity of peer-reviewed publications from countries with assumed high prevalence. This SLR demonstrated a lack of systematic knowledge and a need to provide uniform data collection on SCD prevalence and mortality.

Epidemiology of rare diseases in Brazil: protocol of the Brazilian Rare Diseases Network (RARAS-BRDN)

The Brazilian Policy of Comprehensive Care for People with Rare Diseases (BPCCPRD) was established by the Ministry of Health to reduce morbidity and mortality and improve the quality of life of people with rare diseases (RD). Several laboratory tests, most using molecular genetic technologies, have been incorporated by the Brazilian Public Health System, and 18 specialised centres have so far been established at university hospitals (UH) in the capitals of the Southern, Southeastern and Northeastern regions. However, whether the available human and technological resources in these services are appropriate and sufficient to achieve the goals of care established by the BPCCPRD is unknown. Despite great advances in diagnosis, especially due to new technologies and the recent structuring of clinical assessment of RD in Brazil, epidemiological data are lacking and when available, restricted to specific disorders. This position paper summarises the performance of a nationally representative survey on epidemiology, clinical status, and diagnostic and therapeutic resources employed for individuals with genetic and non-genetic RD in Brazil. The Brazilian Rare Disease Network (BRDN) is under development, comprising 40 institutions, including 18 UH, 17 Rare Diseases Reference Services and five Newborn Screening Reference Services. A retrospective study will be initially conducted, followed by a prospective study. The data collection instrument will use a standard protocol with sociodemographic data and clinical and diagnostic aspects according to international ontology. This great collaborative network is the first initiative of a large epidemiological data collection of RD in Latin America, and the results will increase the knowledge of RD in Brazil and help health managers to improve national public policy on RD in Brazil.

The effects of old and recent migration waves in the distribution of HBB*S globin gene haplotypes

Sickle cell hemoglobin is the result of a mutation at the sixth amino acid position of the beta (β) globin chain. The HBB*S gene is in linkage disequilibrium with five main haplotypes in the β-globin-like gene cluster named according to their ethnic and geographic origins: Bantu (CAR), Benin (BEN), Senegal (SEN), Cameroon (CAM) and Arabian-Indian (ARAB). These haplotypes demonstrated that the sickle cell mutation arose independently at least five times in human history. The distribution of βS haplotypes among Brazilian populations showed a predominance of the CAR haplotype. American populations were clustered in two groups defined by CAR or BEN haplotype frequencies. This scenario is compatible with historical records about the slave trade in the Americas. When all world populations where the sickle cell gene occurs were analyzed, three clusters were disclosed based on CAR, BEN or ARAB haplotype predominance. These patterns may change in the next decades due to recent migrations waves. Since these haplotypes show different clinical characteristics, these recent migrations events raise the necessity to develop optimized public health programs for sickle cell disease screening and management.

High Frequency of Hb E-Saskatoon (HBB: c.67G > A) in Brazilians: A New Genetic Origin?

Hb E-Saskatoon [β22(B4)Glu→Lys, HBB: c.67G > A] is a rare, nonpathological β-globin variant that was first described in a Canadian woman of Scottish and Dutch ancestry and has since then been detected in several populations. The aim of the present study was to identify the origin of Hb E-Saskatoon in Brazil using β-globin haplotypes and genetic ancestry in carriers of this hemoglobin (Hb) variant. Blood samples were investigated by isoelectric focusing (IEF) and high performance liquid chromatography (HPLC) using commercial kits. Hb E-Saskatoon was confirmed by amplification of the HBB gene, followed by sequence analysis. Haplotypes of the β-globin gene were determined by polymerase chain reaction (PCR), followed by digestion with specific restriction enzymes. Individual ancestry was estimated with 48 biallelic insertion/deletions using three 16-plex PCR amplifications. The IEF pattern was similar to Hbs C (HBB: c.19G > A) and Hb E (HBB: c.79G > A) [isoelectric point (pI): 7.59-7.65], and HPLC results showed an elution in the Hb S (HBB: c.20A > T) window [retention time (RT): 4.26-4.38]. DNA sequencing of the amplified β-globin gene showed a mutation at codon 22 (GAA>AAA) corresponding to Hb E-Saskatoon. A total of 11 cases of this variant were identified. In nine unrelated individuals, Hb E-Saskatoon was in linkage disequilibrium with haplotype 2 [+ - - - -]. All subjects showed a high degree of European contribution (mean = 0.85). Hb E-Saskatoon occurred on the β-globin gene of haplotype 2 in all Brazilian carriers. These findings suggest a different genetic origin for this Hb variant from that previously described.

Alpha chain hemoglobins with electrophoretic mobility similar to that of hemoglobin S in a newborn screening program

Objective

To characterize alpha-chain variant hemoglobins with electric mobility similar to that of hemoglobin S in a newborn screening program.

Methods

β^S allele and alpha-thalassemia deletions were investigated in 14 children who had undefined hemoglobin at birth and an electrophoretic profile similar to that of hemoglobin S when they were six months old. Gene sequencing and restriction enzymes (DdeI, BsaJI, NlaIV, Bsu36I and TaqI) were used to identify hemoglobins. Clinical and hematological data were obtained from children who attended scheduled medical visits.

Results

The following alpha chain variants were found: seven children with hemoglobin Hasharon [alpha2 47(CE5) Asp>His, HbA2:c.142G>C], all associated with alpha-thalassemia, five with hemoglobin Ottawa [alpha1 15(A13) Gly>Arg, HBA1:c.46G>C], one with hemoglobin St Luke's [alpha1 95(G2) Pro>Arg, HBA1:c.287C>G] and another one with hemoglobin Etobicoke [alpha212 84(F5) Ser>Arg, HBA212:c.255C>G]. Two associations with hemoglobin S were found: one with hemoglobin Ottawa and one with hemoglobin St Luke's. The mutation underlying hemoglobin Etobicoke was located in a hybrid α212 allele in one child. There was no evidence of clinically relevant hemoglobins detected in this study.

Conclusion

Apparently these are the first cases of hemoglobin Ottawa, St Luke's, Etobicoke and the α212 gene described in Brazil. The hemoglobins detected in this study may lead to false diagnosis of sickle cell trait or sickle cell disease when only isoelectric focusing is used in neonatal screening. Additional tests are necessary for the correct identification of hemoglobin variants.

Hb Stanleyville-II [α78(EF7)Asn→Lys (α2); HbA2: c.237C>A]: incidence of 1:11,500 in a newborn screening program in Brazil

Almost 3 million babies were tested in a newborn screening program in Minas Gerais, Brazil (1998-2008); 128 who have S-like hemoglobins (Hbs) were tested for the β(S) allele and 112 were identified through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or sequencing. Hb Stanleyville-II [α78(EF7)Asn→Lys (α2); HbA2: c.237C>A] was present in 96 children (85.7%), two in a homozygous state and 94 in a heterozygous state. Its estimated prevalence was 1:11,500. Hbs Hasharon [α47(CE5)Asp→His, GAC>CAC (α2)], Ottawa [α15(A13)Gly→Arg (GGT>CGT) (α2 or α1)], G-Ferrara [β57(E1)Asn→Lys (AAC>AAA or AAG)], St. Luke's [α95(G2)Pro→Arg, C CG>C GG (α1)], Maputo [β47(CD6)Asp→Tyr (GAT>TAT)] and Etobicoke [α84(F5)Ser→Arg (AG C>AG G or CGC or AGA) (α2 or α1)] were also identified. Many children with Hbs Stanleyville-II and Hasharon also co-inherited the -α(3.7) thalassemia gene. African ancestry was recognized by parents of all 31 children with Hb Stanleyville-II who were interviewed. Mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) values were significantly lower in children with α-thalassemia (α-thal). We came to the conclusion that Hb Stanleyville-II is not so uncommon in Brazil and seems to have originated from the African slave trade. This study reinforces the importance of an accurate diagnosis of variants that have electrophoretic mobility similar to Hb S [β6(A3)Glu→Val, GAG>GTG] so that false diagnoses are avoided.

Homozygous Hb Stanleyville-II [alpha2 78(EF7) Asn>Lys; HBA2:c.237C>A, not C>G] associated with genotype -α 3.7/-α 3.7 in two Brazilian families

INTRODUCTION

Several hemoglobin variants have electrophoretic behavior similar to hemoglobin S, which may lead to false diagnosis for sickle-cell disorders in newborn screening programs. A homozygous hemoglobin with S mobility was detected in two unrelated babies in Brazil.

METHODS

Isoelectric focusing and high-performance liquid chromatography assays, gene sequencing, and restriction fragment length polymorphism with AfeI were used to characterize the hemoglobin.

RESULTS

Hb Stanleyville-II and -α(3.7) /-α(3.7) type I deletion in the α-globin gene was diagnosed. Parents were heterozygous for both Hb Stanleyville-II and α-thalassemia. Hypochromia and microcytosis were probably due to the homozygous α-thalassemia.

CONCLUSION

Stanleyville-II gene mutation is HBA2:c.237C>A, or C>G, and this information on the Globin Gene Server should be updated; AfeI test is a fast and accurate method to detect it; NBS programs should consider the possibility of Hb Stanleyville-II whenever IEF shows one band in the HbS position, and another one between S and C.