title: A stepwise α-thalassemia screening strategy in high-prevalence areas.
abstract: BACKGROUND
  Coinheritance of α-thalassemia influences the clinical and hematological phenotypes of β-hemoglobinopathies (β-thalassemia and sickle cell disease) and when present together in significant frequency within a population, a spectrum of clinical forms is observed. Precise molecular characterization of α-thalassemia is important in understanding their disease-modifying role in β-hemoglobinopathies and for diagnostic purposes.
  
  
  METHODS
  Because currently used approaches are labor/cost-intensive, time-consuming, error-prone in certain genotype combinations and not applicable for large epidemiological screening, we developed a systematic stepwise strategy to overcome these difficulties. We successfully applied this to characterize the α-globin gene status in 150 Omani cord blood samples with Hb Barts and 32 patients with HbH disease.
  
  
  RESULTS
  We observed a good correlation between α-globin genotypes and level of Hb Bart's with the Hb Bart's levels significantly higher in both deletional and non-deletional α-globin genotypes. The most common α-globin genotype in HbH cases was α(TSaudi) α/α(TSaudi) α (n = 16; 50%) followed by -α(3.7) /-(MED) (n = 10; 31%). This approach detects also the α-globin gene triplication as exemplified by the study of a family where the β-globin gene defect failed to explain the β-thalassemia intermedia phenotype.
  
  
  CONCLUSIONS
  Molecular characterization of α-thalassemia is complex due to high sequence homology between the duplicated α-globin genes and to the existence of a variety of gene rearrangements (small and large deletions of various sizes) and punctual substitutions (non-deletional alleles). The novelty of our strategy resides, not in the individual technical steps per se but in the reasoned sequential order of their use taking into consideration the hematological phenotype as well.
authors.affiliation: Sultan Qaboos University and Hospital, Muscat, Oman.
authors.forename: Salam S
authors.initials: SS
authors.lastname: Alkindi
authors.forename: Shoaib
authors.initials: S
authors.lastname: Alzadjali
authors.forename: Shahina
authors.initials: S
authors.lastname: Daar
authors.forename: Eunice
authors.initials: E
authors.lastname: Sindhuvi
authors.forename: Yasser
authors.initials: Y
authors.lastname: Wali
authors.forename: Anil V
authors.initials: AV
authors.lastname: Pathare
authors.forename: Suresh
authors.initials: S
authors.lastname: Venugopal
authors.forename: Claudine
authors.initials: C
authors.lastname: Lapoumeroulie
authors.forename: Alok
authors.initials: A
authors.lastname: Srivastava
authors.forename: Rajagopal
authors.initials: R
authors.lastname: Krishnamoorthy
mesh_terms: D004909:Erythrocyte Indices; D023061:Gene Order; D005820:Genetic Testing / Q000379:methods; D005838:Genotype; D006801:Humans; D010375:Pedigree; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D015995:Prevalence; D055542:alpha-Globins / Q000235:genetics; D017085:alpha-Thalassemia / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics; D017086:beta-Thalassemia / Q000175:diagnosis / Q000235:genetics
chemical_list: D055542:alpha-Globins
keywords: GeneScan; HbH; newborn; α-thalassemia