Prospective screening for δ-hemoglobinopathies associated with decreased hemoglobin A2 levels or hemoglobin A2 variants: A single center experience.

BACKGROUND: δ-hemoglobinopathies may lead to misdiagnosis of several thalassemia syndromes especially ß-thalassaemia carrier, it is important to evaluate the δ-globin gene defects in areas with high prevalence of globin gene disorders. We describe a prospective screening for δ-hemoglobinopathies in a routine setting in Thailand. METHODS: Study was done on a cohort of 8,471 subjects referred for thalassemia screening, 317 (3.7%) were suspected of having δ-globin gene defects due to reduced hemoglobin (Hb) A2 levels and/or appearance of Hb A2-variants on hemoglobin analysis. Hematologic and DNA analysis by PCR and related assays were carried out. RESULTS: DNA analysis of δ-globin gene identified seven different δ-globin mutations in 24 of 317 subjects (7.6%). Both known mutations; δ-77(T>C) (n = 3), δ-68(C>T) (n = 1), δ-44(G>A) (n = 8), Hb A2-Melbourne (n = 5), δIVSII-897(A>C) (n = 5), and Hb A2-Troodos (n = 1) and a novel mutation; the Hb A2-Roi-Et (n = 1) were identified. This Hb A2-Roi-Et, results from a double mutations in-cis, δCD82(AAG>AAT) and δCD133(GTG>ATG), was interestingly found in combination with an in trans, 12.6 kb deletional δß0-thalassemia in an adult Thai woman who had no Hb A2 and elevated Hb F. A multiplex-allele-specific PCR was developed to detect these novel δ-globin gene defects. CONCLUSIONS: The result confirms a diverse heterogeneity of δ-hemoglobinopathies in Thailand which should prove useful in a prevention and control program of thalassemia in the region.

Quadrupole-Time-of-Flight Mass Spectrometric Identification of Hemoglobin Subunits α, ß, γ and δ in Unknown Peaks of High Performance Liquid Chromatography of Hemoglobin in ß-Thalassemias.

This is the first report of quadrupole time-of-flight (Q-TOF) mass spectrometric identification of the hemoglobin (Hb) subunits, α, ß, δ and γ peptides, derived from enzymatic-digestion of proteins in the early unknown peaks of the cation exchange chromatography of Hb. The objectives were to identify the unknown high performance liquid chromatography (HPLC) peaks in healthy subjects and in patients with ß-thalassemia (ß-thal). The results demonstrate the existence of pools of free globin chains in red blood cells (RBCs). The α-, ß-, δ- and γ-globin peptides were identified in the unknown HPLC peaks. The quantification and role of the free globin pool in patients with ß-thal requires further investigation. Identification of all types of Hb subunits in the retention time (RT) before 1 min. suggests that altered Hbs is the nature of these fast-eluting peaks. Relevancy of thalassemias to the protein-aggregation disorders will require review of the role of free globin in the pathology of the disease.

Compromising for carrier detection of beta thalassemia based on measurement of HbA2 levels in unusual cases.

BACKGROUND: An increased HbA2 level is the hallmark for identification of ß thalassemia carriers. However, in some carriers the level of HbA2 is not typically elevated creating difficulties in making a diagnosis. METHODS: We describe a family having an affected child referred to us for confirmation of diagnosis of ß thalassemia. RESULTS: The father has a classical ß thalassemia trait and the mother showed typical reduced red cell indices with a high RBC count but the HbA2 level was normal (2.4%). On molecular analysis she was a heterozygous carrier having IVS1 nt 5 (G→C) ß thalassemia mutation. Further analysis of δ globin gene showed that the reduction in HbA2 was due to the presence of the δ mutation HbA2 Pelendri [CD 141(Leu→Pro, CTG→CCG)]. CONCLUSIONS: The diagnosis of a ß thalassemia carrier could have been compromised, and states the importance of comprehensive molecular analysis for accurate diagnosis in couples where one partner has ß thalassemia trait.