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Satthakarn S, Panyasai K, Phasit A, Panyasai S. Reliability of hemoglobin A 2 value as measured by the Premier Resolution system for screening of β-thalassemia carriers. Clin Chem Lab Med 2024; 62:453-463. [PMID: 37845805 DOI: 10.1515/cclm-2023-1006] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Accepted: 09/30/2023] [Indexed: 10/18/2023]
Abstract
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.
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Affiliation(s)
- Surada Satthakarn
- Faculty of Allied Health Sciences, Burapha University, Chonburi, Thailand
| | - Kesorn Panyasai
- Department of Occupational Medicine, Lampang Hospital, Lampang, Thailand
| | - Amphai Phasit
- Department of Medical Technology, Lampang Hospital, Lampang, Thailand
| | - Sitthichai Panyasai
- Department of Medical Technology, School of Allied Health Sciences, University of Phayao, Muang Phayao, Phayao, Thailand
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Chin H, Benton MC, Yang L, Poon KS, Tan KML, Jamuar SS, Foo R, Law HY, Goh DL, Chong SS, de Sessions PF. Clinical application of targeted long read sequencing in prenatal beta-thalassemia testing and genetic counseling. Mol Genet Genomic Med 2024; 12:e2285. [PMID: 37740604 PMCID: PMC10767580 DOI: 10.1002/mgg3.2285] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Revised: 08/18/2023] [Accepted: 09/07/2023] [Indexed: 09/24/2023] Open
Abstract
BACKGROUND Beta thalassemia, related to HBB mutation and associated with elevated hemoglobin A2 (HbA2), is an important genetic hemoglobinopathy with high incidences of disease and carrier rates in Singapore. Carrier screening is essential to facilitate prenatal counseling and testing. However, when individuals with elevated HbA2 do not have an identifiable HBB disease-associated variant, there is ambiguity on risk to their offspring. METHODS We describe a case report of a proband with elevated HbA2, no identifiable HBB disease-associated variant, whose partner was a beta thalassemia carrier. Through clinical HBB gene sequencing, multiplex ligation-dependent probe amplification (MLPA) analysis, as well as targeted Nanopore long read sequencing of selected genes, we performed a complete analysis of HBB including the promoter region, 5'UTR and coding gene sequence, as well as evaluation for potential modifier variants and other rare structural variants. RESULTS This process identified that the proband was heterozygous for KLF1:c.544T>C (p.Phe182Leu), a potential functional polymorphism previously known to be associated with benign elevated HbA2 levels. The presence of disease variants in the HBB locus was excluded. CONCLUSION This finding provided clarity and enabled family planning for the proband and her family.
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Affiliation(s)
- Hui‐Lin Chin
- Division of Genetics and Metabolism, Department of PaediatricsKhoo Teck Puat‐National University Children's Medical Institute, National University HospitalSingaporeSingapore
- Department of Paediatrics, Yong Loo Lin School of MedicineNational University of SingaporeSingaporeSingapore
| | | | - Lin Yang
- Oxford Nanopore TechnologiesSingaporeSingapore
| | - Kok Siong Poon
- Department of Laboratory MedicineNational University HospitalSingaporeSingapore
| | - Karen M. L. Tan
- Department of Laboratory MedicineNational University HospitalSingaporeSingapore
| | - Saumya S. Jamuar
- Genetics Service, Department of PaediatricsKK Women's and Children's HospitalSingaporeSingapore
| | - Roger Foo
- Cardiovascular Research Institute, Yong Loo Lin School of MedicineNational University of SingaporeSingaporeSingapore
| | - Hai Yang Law
- DNA Diagnostic and Research LaboratoryKK Women's and Children's HospitalSingaporeSingapore
| | - Denise Li‐Meng Goh
- Division of Genetics and Metabolism, Department of PaediatricsKhoo Teck Puat‐National University Children's Medical Institute, National University HospitalSingaporeSingapore
- Department of Paediatrics, Yong Loo Lin School of MedicineNational University of SingaporeSingaporeSingapore
| | - Samuel S. Chong
- Department of Paediatrics, Yong Loo Lin School of MedicineNational University of SingaporeSingaporeSingapore
- Department of Laboratory MedicineNational University HospitalSingaporeSingapore
- Department of Obstetrics and GynaecologyYong Loo Lin School of Medicine, National University of SingaporeSingaporeSingapore
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Tang XW, Jiang F, Li J, Lin XM, Zhou JY, Wan JH, Zuo LD, Qu YX, Li FT, Chen GL, Li DZ. Application of real-time PCR-based multicolor melting curve with automatic analysis system in pregestational and prenatal thalassemia diagnoses. Ann Hum Genet 2023; 87:316-325. [PMID: 37771257 DOI: 10.1111/ahg.12531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 09/07/2023] [Accepted: 09/12/2023] [Indexed: 09/30/2023]
Abstract
BACKGROUND To evaluate the value of the real-time PCR-based multicolor melting curve analysis (MMCA) with an automatic analysis system used in a mass thalassemia screening and prenatal diagnosis program. METHODS A total of 18,912 peripheral blood samples from 9456 couples and 1150 prenatal samples were detected by MMCA assay. All prenatal samples were also tested by a conventional method. Samples with unknown melting peaks, unusual peak height ratios between a wild allele and a mutant allele, or a discordant phenotype-genotype match were further studied by using multiplex ligation-dependent probe amplification (MLPA) or Sanger sequencing. All MMCA results were automatically analyzed and manually checked. The consistency between MMCA assay and conventional methods among prenatal samples was investigated. RESULTS Except for initiation codon (T > G) (HBB:c.2T > G), all genotypes of thalassemia inside the scope of conventional methods were detected by MMCA assay. Additionally, 27 carriers with 10 rare HBB variants, 13 with α fusion gene, 1 with a rare deletion in α globin gene, and 1 with rare HBA variant were detected by using MMCA assay. CONCLUSION MMCA can be an alternative approach used in routine thalassemia carrier screening and prenatal diagnosis for its high throughput, sufficient stability, low cost, and easy operation.
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Affiliation(s)
- Xue-Wei Tang
- Prenatal Diagnostic Center, Guangzhou Women and Children's Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Fan Jiang
- Prenatal Diagnostic Center, Guangzhou Women and Children's Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Jian Li
- Prenatal Diagnostic Center, Guangzhou Women and Children's Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Xiao-Mei Lin
- Prenatal Diagnostic Center, Guangzhou Women and Children's Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Jian-Ying Zhou
- Prenatal Diagnostic Center, Guangzhou Women and Children's Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Jun-Hui Wan
- Prenatal Diagnostic Center, Guangzhou Women and Children's Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Lian-Dong Zuo
- Prenatal Diagnostic Center, Guangzhou Women and Children's Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Yan-Xia Qu
- Prenatal Diagnostic Center, Guangzhou Women and Children's Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Fa-Tao Li
- Prenatal Diagnostic Center, Guangzhou Women and Children's Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Gui-Lan Chen
- Prenatal Diagnostic Center, Guangzhou Women and Children's Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Dong-Zhi Li
- Prenatal Diagnostic Center, Guangzhou Women and Children's Medical Center affiliated to Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
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Lou J, Ye Y, Sun M, Zhao Y, Fu Y, Liu Y. A stepwise haematological screening and whole-exome sequencing reveal multiple mutations from SUPT5H causing an elevation of Hb A 2 from a cohort of 47336 individuals. Int J Lab Hematol 2023; 45:90-95. [PMID: 36054783 DOI: 10.1111/ijlh.13959] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Accepted: 08/10/2022] [Indexed: 01/18/2023]
Abstract
INTRODUCTION Though an increase in Hb A2 is one of the most key markers of β-thal carriers, a few independent cases are reported to show elevated Hb A2 levels caused by mutations in other genes beyond β-globin gene. METHODS We reviewed the haematological indices of 47336 individuals to analyse the phenotype-genotype correlation and identified 1439 individuals (3.04%) positive in the elevation of Hb A2 . Globin and KLF1 genes analysis was performed, and further whole-exome sequencing was carried to dissect the genetic causes of those positive samples without β-thalassemic or KLF1 mutations. RESULTS Of these 1439 individuals with elevated Hb A2 , 1381 had a molecular defect in globin genes, and most were β-thalassemic mutation; 10 had a molecular defect in KLF1 gene. Finally, among the 38 individuals without β-thalassemic or KLF1 mutations, 7 were identified to carried a loss-of-function mutation in SUPT5H. CONCLUSION This study has provided a mutation spectrum of SUPT5H in a cohort screening leading to the elevation of Hb A2 . According to the previous observations that individuals with a combination of β-thal mutation and a SUPT5H variant might present moderate β-thaelassemia, these findings emphasized the importance of comprehensive molecular diagnosis to prevent birth defects of β-thaelassemia caused by rare mutations from modifier genes.
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Affiliation(s)
- Jiwu Lou
- Prenatal Diagnostic Center, Dongguan Maternal and Children Health Hospital, Dongguan, Guangdong, People's Republic of China
| | - Yuhua Ye
- Department of Medical Genetics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong, People's Republic of China.,Guangdong Genetics Testing Engineering Research Center, Guangzhou, Guangdong, People's Republic of China.,Innovation Center for Diagnostics and Treatment of Thaelassemia, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Manna Sun
- Department of Obstetrics & Gynecology, Dongguan Maternal and Children Hospital, Dongguan, Guangdong, People's Republic of China
| | - Ying Zhao
- Prenatal Diagnostic Center, Dongguan Maternal and Children Health Hospital, Dongguan, Guangdong, People's Republic of China
| | - Youqing Fu
- Prenatal Diagnostic Center, Dongguan Maternal and Children Health Hospital, Dongguan, Guangdong, People's Republic of China
| | - Yanhui Liu
- Prenatal Diagnostic Center, Dongguan Maternal and Children Health Hospital, Dongguan, Guangdong, People's Republic of China
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Colaco S, Nadkarni A. Borderline HbA 2 levels: Dilemma in diagnosis of beta-thalassemia carriers. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2021; 788:108387. [PMID: 34893152 DOI: 10.1016/j.mrrev.2021.108387] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 05/27/2021] [Accepted: 06/08/2021] [Indexed: 12/17/2022]
Abstract
There is inconsistency in the exact definition of diagnostic levels of HbA2 for β thalassemia trait. While many laboratories consider HbA2 ≥4.0 % diagnostic, still others consider HbA2 ≥3.3 % or HbA2 ≥3.5 % as the cut-off for establishing β thalassemia carrier diagnosis. This is because, over the years, studies have described β thalassemia carriers showing HbA2 levels that lie above the normal range of HbA2 but below the typical carrier range of β thalassemia. These, "borderline HbA2 levels", though not detrimental to health, are significant in β thalassemia carrier diagnosis because they can lead to misinterpretation of results. In this review, we have evaluated the prevalence of borderline HbA2 levels and discussed the causes of borderline HbA2 values. We have also compiled an extensive catalogue of β globin gene defects associated with borderline HbA2 levels and have discussed strategies to avoid misdiagnosing borderline HbA2 β thalassemia carriers. Our analysis of studies that have delineated the cause of borderline HbA2 levels in different populations shows that 35.4 % [626/1766] of all individuals with borderline HbA2 levels carry a molecular defect. Among the positive samples, 17 % [299/1766] show β globin gene defects, 7.7 % [137/1766] show α thalassemia defects, 2.7 % [49/1766] show KLF1 gene mutations, 2.3 % [41/1766] show the co-inheritance of β and α thalassemia, 2.0 % [37/1766] show the co-inheritance of β and δ thalassemia and 1.8 % [32/1766] show α globin gene triplication. It appears that a comprehensive molecular work up of the β globin gene is the only definite method to detect borderline HbA2 β thalassemia carriers, especially in populations with a high prevalence of the disease. The presence of associated genetic or acquired determinants may subsequently be assessed to identify the cause of borderline HbA2.
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Affiliation(s)
- Stacy Colaco
- Department of Hematogenetics, ICMR-National Institute of Immunohematology, 13th Floor, K.E.M. Hospital Campus, Parel, Mumbai, 400 012, India
| | - Anita Nadkarni
- Department of Hematogenetics, ICMR-National Institute of Immunohematology, 13th Floor, K.E.M. Hospital Campus, Parel, Mumbai, 400 012, India.
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Luo LP, Ma L, Lin SB, Huang JG. Elevated Hb A 2 is Not Always Indicative of β-Thalassemia. Hemoglobin 2021; 45:186-190. [PMID: 34100337 DOI: 10.1080/03630269.2021.1936008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Hb A2 levels are usually high in carriers of β-thalassemia (β-thal). These levels also provide a sensitive marker for the identification of hemoglobin (Hb) variants. In this study, we aimed to examine two patients from two Chinese families who showed elevated Hb A2 levels but did not show any signs of β-thal. The HBB variants were analyzed using direct sequencing of HBB and in silico prediction analysis. Moreover, the family's genetic history was investigated. We examined two probands from different Chinese families with elevated Hb A2 levels who were not afflicted with β-thal, although several nucleotide changes were found at codon 81 (CTC>CTA) (HBB: c.246C>A) in Family 1 and a compound heterozygosity for codon 40 (AGG>AAG) (HBB: c.122G>A) and IVS-II-478 (C>A) (HBB: c.316-373C>A) in Family 2. After investigating the genetic history of both families including the β-thal aspect, we found that these mutations were not responsible for the elevated Hb A2 levels. It is rarely reported that high Hb A2 level is not indicative of β-thal. In contrast, low or normal Hb A2 level is always found with β-thal due to other molecular defects that mask their β-thal genotype. Our results highlight the importance of considering the genetic factors related and unrelated to β-thal to improve the accuracy of future genetic counseling.
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Affiliation(s)
- Li-Ping Luo
- Department of Gynaecology and Obstetrics, Ganzhou Maternal and Child Health Hospital, Ganzhou, Jiangxi Province, People's Republic of China
| | - Li Ma
- Department of Gynaecology and Obstetrics, Ganzhou Maternal and Child Health Hospital, Ganzhou, Jiangxi Province, People's Republic of China
| | - Shao-Bin Lin
- Fetal Medicine Centre, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong Province, People's Republic of China
| | - Jun-Gao Huang
- Department of Medical Genetics, Ganzhou Maternal and Child Health Hospital, Ganzhou, Jiangxi Province, People's Republic of China
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