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Objective To discover the mutations of rare thalassemia genes by sequencing of α and β-globin genes,to understand the frequency of rare mutations and to enrich thalassemia gene mutation spectrum in Chinese population.Methods For the cases of phenotype and genotype inconsistent,the 1st generation of sequencing was performed for α or β-globin gene coding region sequence analysis.Results A total of 102 patients with rare thalassemia gene mutations were found by sequencing,including 79 cases of β-thalassemia with 35 kinds of mutant types,and 23 cases of α-thalassemia with 11 kinds of mutant types.Conclusion The thalassemia gene sequencing could reveal rare mutations in genes,identify the genotype of patients,provide important support for prenatal diagnosis of rare thalassemia families,and reduce the missing rate and birth rate of children with thalassemia.
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ObjectivesTo explore the roles of mean corpuscular volume(MCV),mean corpuscular hemoglobin(MCH) and hemoglobin A2 (HbA2) in the laboratory screening of thalassemia,and to find optimal screening modality for different conditions.Methods From September 2008 to May 2011,1384 subjects underwent thalassemia screening at Department of Obstertrics andGynecology of Nanfang Hospital.Of them,1036 cases were diagnosed with thalassemia (408 α-thalassemia,608 β-thalassemia,and 20 αβ compound thalassemia,thalassemia group) and 348 without thalassemia,non-thalassemia group.All subjects were screened respectively for MCV,MCH and HbA2.Analyses were performed in all subjects to assess the sensitivity,specificity,positive predictive value,negative predictive value and diagnostic accuracy respectively associated with MCV,MCH and HbA2 alone,combination of MCV and MCH,and combination of MCV,MCH and HbA2.Results( 1 ) In the thalassemia group,the sensitivity of MCV alone was 92.9％ (379/408) for α thalassemia,99.3％ (604/608) for β thalassemia and 100.0％(20/20) for αβ compound thalassemia.In the non-thalassemia group,the specificity of MCV alone was 75.0％ (261/348).(2) In the thalassemia group,the sensitivity of MCH alone was 92.9％ (379/408) in α thalassemia,99.0％ (602/608) in β thalassemia and 100.0％ (20/20) in αβ compound thalassemia.In the non-thalassemia group,the specificity of MCH alone was 72.7 ％ (253/348).(3) The sensitivity of Hb A2 alone was 67.4％ (275/408) for α thalassemia,97.5％ (593/608) for 3 thalassemia,and 100％ (20/20) for α3 compound thalassemia while it's specificity was 72.4％ (252/348) in the non-thalassemia group.(4)With positive indexes of MCV,MCH and MCV + MCH,when HbA2 ＞ 3.5％ it had a high value in [β-thalassemia screening,but when HbA2 ＜ 2.5％ it had little value in α-thalassemia screening.(5) As a single marker,MCV and MCH had better sensitivity,specificity,positive predictive value,negative predictive value and diagnosis accuracy than HbA2.MCV + MCH was the best for overall screening,but for [β thalassemia screening,MCV + MCH + HbA2 was the best.ConclusionsMCV and MCH are suitable for epidemic screening in a large population,physical examination and premarital check-up.Hb electrophoresis andthalassemiagenediagnosisarerecommendedforsubjectswithpositiveMCVandMCH indexes.Diagnoses of α and β-thalassemia gene are recommended for pregnant women with positive MCV and MCH indexes.
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Objective To summarize the geographical distribution,phenotype and genotype data of 206 thalassemia families underwent prenatal diagnosis to provide information for clinical genetic counseling and avoid the birth of severe thalassemia children.MethodsTotally,206 thalassemia families were collected from Southern Medical University Nanfang Hospital from January 2008 to December 2009.Genomic DNA was extracted from peripheral blood,villus,amniotic fluid or cord blood from the couples or the fetuses.Gap-polymerase chain reaction (gap-PCR) and reverse dot blot (RDB) technology were used to detect the common α and β-thalassemia mutations.DNA sequencing was used to detect the rare mutations.Follow-up visit were done half a year after the fetuses were born. Results The 206 thalassemia families came from 12 provinces and areas across China,including Heilongjiang province.Mutations detected in α-thalassemia families included --SEA/,-α3.7/,-α4.2/,αCS α/ and αQS α/,which were all included in the testing kit. While there were 4 kinds of β-thalassemia mutations,Gγ+ (A γδβ)0,-28(A→C),CD54-58(-TATGGGCAACCCT) and CD37(G→A),could not be identified with routine testing kit. The 57 α-thalassemia families consisted of 11(19.3％) severe thalassemia,induding 8 Bart's hydrops syndrome and 3 Hb H disease,26(45.6％) heterozygote and 20(35.1％) normal infants,and the 149 β-thalassemia majors families consisted of 28 (18.8％) severe thalassemia,82(55.0％) heterozygote and 39 (26.2％) normal infants.Among the β-thalassemia heterozygotes,there was one 13-trisomy.Follow-up visit found that babies with Bart ' s hydrops syndrome (n =8),Hb H disease (n =3),β-thalassemia majors (n =28) and β thalassemia heterozygote combined with 13-trisomy(n=1) were aborted.Conclusions Thalassemia was found in some north area other than south of China,which should be paid more attention by clinicians.Gap-PCR and PCR-RDB technology are effective measures for thalassemia prenatal diagnosis in identifying major thalassemia fetuses before their birth,thus reduce the birth rate of thalassemia baby.But missed diagnosis might exist during the screening,so it is necessary to perform DNA sequencing on those patients with positive symptoms and negative common genetic diagnostic results.At the same time,prenatal diagnosis of chromosomal disorders should not be neglected for high-risk families.