Development of a High Resolution Melting Curve Analysis for the Detection of Hemoglobin δ-Chain Variants in Thailand and Identification of Hb A2-Walsgrave [codon 52 (GAT>CAT), Asp→His; HBD:c.157G>C] in a Pregnant Woman from Southern Thailand.

Background: Delta-chain (δ-chain) variants are a group of rare hemoglobin (Hb) variants resulting from mutations within the δ-globin gene. Although quantification of Hb A2 levels is a useful screening tool for the beta-thalassemia trait, the coinheritance of a δ-globin gene mutation can lead to misinterpretation of diagnostic results. Objective: To identify an unreported Hb A2 variant in Thailand and to develop a high resolution melting (HRM) curve assay for the four δ-globin chain variants found in the Thai population. Materials and Methods: Allele-specific polymerase chain reaction (ASPCR) was used to analyze a total of 18 DNA samples for Hb variants comprising 10 wild-type controls, 4 Hb A2-Melbourne, 1 Hb A2-Lampang, 2 Hb A2-Kiriwong, and an unknown variant via HRM assays. Results: The unreported Hb A2 variant in Thailand was found to be Hb A2-Walsgrave resulting from δ-globin gene mutation at codon 52 (GAT>CAT). This was also confirmed using ASPCR. In addition, we demonstrated that the HRM curve profile for Hb A2-Melbourne, Hb A2-Lampang, Hb A2-Walsgrave, and Hb A2-Kiriwong could be identified so as to distinguish the mutant alleles from one another and from wild-type alleles. Conclusion: This HRM assay detected both known and unknown mutations with simultaneous differentiation between heterozygous and homozygous alleles on a polymerase chain reaction fragment spanning four of the δ-globin variants found in Thailand. This assay may help to support the prevention and control of thalassemias and hemoglobinopathies in Thailand.

Phenotype and Genotype in a Cohort of 312 Adult Patients with Nontransfusion-Dependent Thalassemia in Northeast Thailand.

Patients with nontransfusion-dependent thalassemia (NTDT) do not require regular blood transfusion for survival but may encounter several complications that contribute to morbidity and mortality. We report the molecular heterogeneity and hematological features of NTDT in 312 adult patients in northeast Thailand. Hemoglobin (Hb) and DNA analyses identified 177 subjects with Hb E-ß-thalassemia, 1 with homozygous ß0-thalassemia and 134 with Hb H, AEBart's and EEBart's diseases. For ß-thalassemia, 12 different mutations including both ß0- and ß+-thalassemias were detected. Coinheritance of α-thalassemia as an ameliorating factor was observed in 18 of 178 cases (10.1%) with ß-thalassemia. The α-globin gene triplicated haplotype (αααanti3.7) was observed in 1 case of Hb E-ß0-thalassemia. The presence of the -158 (Cx2192;T) Gx03B3;-XmnI polymorphism (+/+) was found to be associated with increased Hb F expression, but its frequency in the studied subjects was low. Those with α-thalassemia included 17 with deletional and 51 nondeletional Hb H, and 63 with AEBart's and 3 with EEBart's diseases. The hematological parameters of these NTDT and genotype-phenotype relationships are presented. The diverse molecular heterogeneity of NTDT underlines the importance of complete genotyping of the patient. These results should prove useful for management planning, the prediction of clinical outcome and to improve genetic counseling for NTDT patients.

A risk score for predicting pulmonary hypertension in patients with non-transfusion-dependent thalassemia in northeastern Thailand: The E-SAAN score.

INTRODUCTION: Pulmonary hypertension (PH) is a major complication in patients with non-transfusion-dependent thalassemia (NTDT). The risk score was developed to be a screening test for PH risk in these patients. METHODS: A multi-center study was conducted in patients with NTDT aged ≥10 years old. PH risk was defined as tricuspid regurgitation velocity >2.9 m/s by echocardiography. The clinical parameters significantly associated with PH were entered into the logistic regression model. RESULTS: The E-SAAN score included (1) age >35 years (2.5 points), (2) time after splenectomy >5 years (2.5 points), and (3) ß-thalassemia/hemoglobin E (2 points). Using the cut-off point of 4.5 points, the score showed a good discrimination in the validating group with an area under receiver-operating characteristics curve of 0.88 (95% CI 0.8-0.95). CONCLUSION: The E-SAAN score is a simple and practical score which can be used as a screening test for PH risk in patients with NTDT.

Routine screening for α-thalassaemia using an immunochromatographic strip assay for haemoglobin Bart's.

OBJECTIVE: To evaluate an immunochromatographic (IC) strip assay for Hb Bart's as a routine screening test for α-thalassaemia in area with a high prevalence of thalassaemia and haemoglobinopathies. METHODS: A total of 300 adult screen positive blood specimens were collected at an ongoing thalassaemia screening programme in northeast Thailand. Routine screening was done using red blood cell indices, osmotic fragility, and dichlorophenolindophenol tests. The IC strip assay for haemoglobin Bart's was performed on all samples. The result was evaluated against thalassaemia genotypes determined using standard haemoglobin and DNA analyses. RESULTS: Of 300 subjects investigated, Hb and DNA analyses identified 32 with normal genotype. The remaining subjects carried thalassaemia with as many as 16 different genotypes. Hb Bart's was detected in all cases, with several α(0)-thalassaemia (SEA type) related disorders. Of cases with α(+)-thalassaemia, 86.1% showed a positive result; 100 out of 103 Hb E carriers, all homozygous Hb E and ß-thalassaemia trait were negative. Nine out of 17 cases with ß-thalassaemia/Hb E disease, and one case of double heterozygote for Hb Q-Thailand and Hb E returned positive results. The overall sensitivity and specificity of the IC strip assay for detecting α(0)-thalassaemia were 100% and 73.1%, respectively. CONCLUSION: The results showed a high sensitivity for screening for α(0)-thalassaemia using IC strip assay for Hb Bart's. This simple method, used in combination with conventional screening protocols, should lead to a significant reduction in the number of referral cases for DNA analysis. Cost effectiveness in each population should be taken into consideration.

Effect of genotype on pulmonary hypertension risk in patients with thalassemia.

INTRODUCTION: Pulmonary hypertension is one of the major complications in patients with non-transfusion-dependent thalassemia (NTDT). Patients with NTDT have distinct genetic subgroups. Therefore, the effects of different genotype groups on pulmonary hypertension risk in patients with NTDT were assessed. METHODS: A cross-sectional study was conducted in patients with NTDT aged ≥ 10 yr old at Srinagarind University Hospital and Udonthani Hospital, Thailand. Pulmonary hypertension risk was defined as peak tricuspid regurgitation velocity > 2.9 m/s by trans-thoracic echocardiography. Clinical characteristics and laboratory data that literature has indicated as risk factors for pulmonary hypertension were collected. The effect of genotype group on pulmonary hypertension risk was evaluated by using multivariate logistic regression analysis. RESULTS: Of 219 patients, pulmonary hypertension risk was found in 24 patients (10.96%). All patients were categorized into two groups according to genetic data that included: (i) ß-thalassemia (139, 63.5%), (ii) α-thalassemia and combined α and ß-thalassemia (80, 36.5%). Genotype groups were statistically and significantly associated with pulmonary hypertension risk based on the adjusted odds ratios after adjustment for other factors. Patients with ß-thalassemia had a statistically significant higher risk for pulmonary hypertension risk (odds ratio = 9.47, P = 0.036) compared to patients with α-thalassemia and patients with combined α and ß-thalassemia. CONCLUSION: The genotype group is an independent risk factor for pulmonary hypertension in patients with NTDT. Echocardiography should be routinely recommended for all patients with ß-thalassemia. Routine screening in patients with α-thalassemia and combined α and ß-thalassemia, however, may not be necessary or should focus on the older population.