HbA2 levels in β-thalassaemia carriers with the Filipino β0-deletion: are the levels higher than what is found with non-deletional forms of β0-thalassaemia?

AIMS: Classical carriers of β-thalassaemia are identified by a raised HbA2 level. Earlier studies indicated that the Filipino β-deletion has high raised HbA2 levels. The introduction of automated high performance liquid chromatography (HPLC) for thalassaemia screening is an important advance in technology for haematology laboratories. The BioRad Variant II Hb analyser is a common instrument used to quantify HbA2 levels in thalassaemia screening. This study aimed to determine HbA2 levels in carriers of Filipino β-mutation using the BioRad Variant II Hb analyser. METHODS: The Filipino β-deletion was identified using gap-polymerase chain reaction (PCR) in the parents of transfusion dependent β-thalassaemia patients who were homozygous for the Filipino β-deletion in the indigenous population of Sabah, Malaysia. Hb subtypes were quantified on the BioRad Variant II Hb analyser. Concurrent α-thalassaemia was identified by multiplex gap-PCR for deletions and amplification refractory mutation system (ARMS)-PCR for non-deletional mutations. RESULTS: The mean HbA2 level for Filipino β-thalassaemia trait was 5.9 ± 0.47 and with coinheritance of α-thalassaemia was 6.3 ± 0.44 (-α heterozygous) and 6.7 ± 0.36 (-α homozygous). The HbA2 levels were all >4% in keeping with the findings of classical β-thalassaemia trait and significantly higher than levels seen in non-deletional forms of β-thalassaemia. CONCLUSION: The HbA2 level measured on the BioRad Variant II Hb analyser was lower than the level in the first description of the Filipino β-thalassaemia. β-thalassaemia trait with coinheritance of α-thalassaemia (-α) is associated with significantly higher HbA2 level

Detection on common deletional alpha thalassaemia in pregnant women by polymerase chain reaction techniques

Thalassaemia is the most common inherited disorder worldwide and represent as a major health problem in many areas and approximately 4.5%- 6% of Malaysians are carrier of this genetic disorder. There are two type of thalassaemia which α and β thalassemia. α-thalassaemia either the deletion of a single or double α-globin gene deletion that is located at position 16p3.3 is the one of the most common genetic disorder in the world. In Malaysia, the incidence is 4.5%. The aims of this study were to identify and characterised the common deletional type cases of α-thalassaemia in Malay pregnant women at HUSM by molecular method. A total of 200 Malay pregnant women who attended for an antenatal check-up at Hospital Universiti Sains Malaysia were screened for α-thalassaemia. DNA was extracted from 200 pregnant women blood using commercial DNA extraction kit prior to PCR amplification. Of these, 16 were excluded as they were diagnosed as β- thalassaemia/Hb E trait. Out of 184 genomic DNA, 17 (9.2%) were possessed α-thalassaemia deletion. The genotype could be identified to - α3.7/αα in 15 (8.1%) and --SEA/αα in 2(1.1%). While -α4.2 kb deletion and --THAI deletion was not detected in our subjects. Thus, the most common deletion in the Malays pregnant women were -α3.7 followed by --SEA. The molecular method has been established to detect these carriers. The presence of two gene deletion evidenced by --SEA. showed the importance to screen α- thalassaemia among Malay pregnant women and subsequent screening patients' spouse to exclude hydrops fetalis. Detection of --SEA α-thalassaemia by PCR techniques is convenient, and suitable to be used as a confirmatory test

Alpha thalassemia among sickle cell anaemia patients in Kampala, Uganda

Background: Sickle cell anaemia is prevalent in sub Saharan Africa. While α+-thalassaemia is known to modulate sickle cell anaemia, its magnitude and significance in Uganda have hitherto not been described.Objectives: To determine the prevalence of α+thalassaemia among sickle cell anaemia patients in Mulago Hospital and to describe the clinical and laboratory findings in these patients.Methods: A cross sectional study was carried out on patients with sickle cell anaemia in Kampala. Dried blood spots were used to analyze for the deletional α+ thalassaemia using multiplex polymerase chain reaction.Results: Of the 142 patients with sickle cell anaemia, 110 (77.5%) had the αα+thalassaemia deletion. The gene frequency of (-α) was 0.425. Ninety one percent (100/110) of those with α+thalassaemia were heterozygous (αα/α-). Amongst the patients older than 60 months, 15 (83.3%) of those without αα+thalassaemia had significant hepatomegaly of greater than 4 cm compared to 36 (45.6%) of those with α+thalassaemia (p=0.003).Conclusion: The gene frequency of (-α) of 0.425 noted in this study is higher than that reported from many places in Africa. Concurrent alpha thalassemia might be a protective trait against significant hepatomegaly in sickle cell anaemia patients more than 60 months of age at Mulago hospital.Keywords: Alpha thalassemia, sickle cell anaemia patients, Kampala, Ugand

Alpha-thalassaemia trait as a cause of unexplained microcytosis in a South African population

Background. Red cell microcytosis is a common abnormality detected in a full blood count, which often prompts clinicians to investigate further for a cause. In the absence of iron deficiency and anaemia of chronic disease, the differential diagnosis includes β-thalassaemia trait and α-thalassaemia trait.Methods. We investigated the contribution of α-thalassaemia trait in South African subjects with unexplained microcytosis. Iron studies, haemoglobin subfractionation and multiplex polymerase chain reaction (PCR) analysis for α-globin gene deletions were performed on 97 controls and 86 patients.Results. After excluding iron deficiency, anaemia of chronic disease and β thalassaemia trait, 78.0% of subjects with unexplained microcytosis were confirmed on PCR analysis to have α-thalassaemia trait.Conclusion. Alpha-thalassaemia trait accounts for the majority of unexplained microcytosis

NEGATIVE EPISTASIS BETWEEN α+ THALASSAEMIA AND SICKLE CELL TRAIT CAN EXPLAIN INTERPOPULATION VARIATION IN SOUTH ASIA

Recent studies in Kenya and Ghana have shown that individuals who inherit two malaria-protective genetic disorders of haemoglobin—α+ thalassaemia and sickle cell trait—experience a much lower level of malaria protection than those who inherit sickle cell trait alone. We have previously demonstrated that this can limit the frequency of α+ thalassaemia in a population in which sickle cell is present, which may account for the frequency of α+ thalassaemia in sub-Saharan Africa not exceeding 50%. Here we consider the relationship between α+ thalassaemia and sickle cell in South Asian populations, and show that very high levels of α+ thalassaemia combined with varying levels of malaria selection can explain why sickle cell has penetrated certain South Asian populations but not others

Effect of α+-thalassaemia on episodes of fever due to malaria and other causes: a community-based cohort study in Tanzania

It is controversial to what degree α(+)-thalassaemia protects against episodes of uncomplicated malaria and febrile disease due to infections other than Plasmodium. In Tanzania, in children aged 6-60 months and height-for-age z-score < -1.5 SD (n = 612), rates of fevers due to malaria and other causes were compared between those with heterozygous or homozygotes α(+)-thalassaemia and those with a normal genotype, using Cox regression models that accounted for multiple events per child. The overall incidence of malaria was 3.0/child-year (1, 572/526 child-years); no differences were found in malaria rates between genotypes (hazard ratios, 95% CI: 0.93, 0.82-1.06 and 0.91, 0.73-1.14 for heterozygotes and homozygotes respectively, adjusted for baseline factors that were predictive for outcome). However, this association strongly depended on age: among children aged 6-17 months, those with α(+)-thalassaemia experienced episodes more frequently than those with a normal genotype (1.30, 1.02-1.65 and 1.15, 0.80-1.65 for heterozygotes and homozygotes respectively), whereas among their peers aged 18-60 months, α(+)-thalassaemia protected against malaria (0.80, 0.68-0.95 and 0.78, 0.60-1.03; p-value for interaction 0.001 and 0.10 for hetero- and homozygotes respectively). No effect was observed on non-malarial febrile episodes. In this population, the association between α(+)-thalassaemia and malaria depends on age. Our data suggest that protection by α(+)-thalassaemia is conferred by more efficient acquisition of malaria-specific immunity

Comparison of haemoglobin H inclusion bodies with embryonic ζ globin in screening for α thalassaemia

Aims - To compare the haemoglobin (Hb) H inclusion test with immunocytochemical detection of embryonic ζ chains in screening for a thalassaemia. Methods - Blood samples from 115 patients with relevant clinical history and hypochromic microcytic indexes were screened using the HbH inclusion test and the Variant Hemoglobin Testing System (BioRad, Hercules, CA, USA). Results - The HbH inclusion test was positive in 61 of 115 cases, three of whom had HbH disease confirmed by electrophoresis. The remaining 58 had α thalassaemia 1. All three HbH cases and 56 of 58 cases of a thalassaemia 1 expressed embryonic ζ chains, giving a specificity of 96.7%. Fifty four of 115 cases had a negative HbH inclusion test, of whom 50 had β thalassaemia trait and three had iron deficiency. No diagnosis was reached for the remaining patient. Conclusion - The immunocytochemical test is as sensitive as the HbH inclusion test in screening for a thalassaemia. The presence of ζ chains is highly specific for a thalassaemia I incorporating the (--/SEA) deletion. The specificity and simplicity of the immunocytochemical test make it the test of choice in screening for α thalassaemia.published_or_final_versio

α-thalassaemia

Alpha-thalassaemia is inherited as an autosomal recessive disorder characterised by a microcytic hypochromic anaemia, and a clinical phenotype varying from almost asymptomatic to a lethal haemolytic anaemia

Identification of α°-thalassaemia (–SEA) using an enzyme-linked immunosorbent assay (ELISA) for embryonic zeta-globin chain detection – a preliminary study

Objectives: This study aimed to evaluate the UBI MAGIWELTM ζ-GLOBIN ELISA Kit for the presumptive diagnosis of αo-thalassaemia. The ELISA results obtained were confirmed by molecular characterisation of αo-thalassaemia using a Duplex-PCR. Methods: Routine peripheral blood counts and red cell indices were determined in 94 blood samples sent for Hb analysis. Hb subtypes were quantified by high performance liquid chromatography (HPLC) and Hb electrophoresis conducted on agarose gel at pH 8.5. Zeta-globin chain levels were determined using the UBI MAGIWELTM ζ-GLOBIN ELISA Kit. Molecular analysis was performed using a duplex-PCR which simultaneously amplifies a normal 136 bp sequence between the ψα−α2-globin genes and a 730 bp Southeast Asian deletion-specific sequence (–SEA) between the ψα2−θ1-globin genes. Results: Using the ELISA assay kit, 20 blood samples were presumptively identified as α-thalassaemia carriers from elevated ζ-globin chains (OD>0.3) while the remaining 74 blood samples showed OD<0.3. Molecular characterisation confirmed amplification of the 136 bp normal fragment in all the blood samples. Seventeen of the 20 DNA samples from the α-thalassaemia carriers amplified the SEA-deletion specific fragment. The remaining three DNA samples did not amplify the SEA-deletion specific fragment but amplified the normal α-globin gene sequence, indicating the presence of amplifiable DNA in these samples. Further molecular characterisation of the α-3.7 and -α4.2 deletions and Hb Constant Spring (CS) mutation showed the absence of these defects in these 3 DNA samples. Conclusion: This preliminary investigation showed the sensitivity and specificity of the UBI MAGIWEL ζ-globin ELISA kit as 100 % and 96.1 % respectively in the detection of α-thalassaemia-1 carriers (–SEA)