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Objective: To conduct research of beta-Thalassemia incidence and genotypes on children below 7 years of age in Nanning, Liuzhou and Baise areas, Guangxi province., Methods: A total of 2261 children aged below 7 in Nanning, Liuzhou and Baise areas were studied. Venous blood was detected by routine blood test, hemoglobin analysis and beta-Thalassemia genotyping., Results: Among 2261 samples, 125 showed high level of HbA2 and were diagnosed as beta-Thalassemia (5.53%). Genotypes of the patients were classified as: 59 cases with beta-globin gene condon (CD) 41-42 mutation, 33 cases CD17 mutation, 18 cases with TA TA box nt-28 mutation, 7 with IVS-II-654 mutation, 3 with CD43 mutation, 3 with HbE mutation, one with CD71-72 and TATA box nt-29 mutation, respectively. The genotyping frequencies of beta-Thalassemia were as follows: 47.20% for CD41-42 mutation, 26.40% for CD17 mutation, 14.40% for TATAbox nt-28 mutation, 5.60% for IVS-II-654 mutation, 2.40% for CD43 mutation, 2.40% for HbE mutation, 0.80% for CD71-72 mutation and TATAbox nt-29 mutation respectively., Conclusion: This study on children in the area with high incidence of beta-Thalassemia reflected the incidence and characteristics of genotypes in this area. Our data also provided evidence for the development of a program on genetic counseling and prevention for thalassemia.

Objective: To investigate non-invasive prenatal genetic diagnosis of beta-thalassaemia using a single fetal nucleated erythrocyte (NRBC) from maternal blood by comparing with the genotype obtained from chorionic villus or amniocytes, and to evaluate the diagnostic results in reliability and feasibility of this method., Methods: Maternal blood samples were obtained from 28 pregnant women at risk of beta thalassaemia during 9 - 34 weeks of gestation. NRBCs in maternal blood were enriched by single density gradient separation, stained with benzidine, and then collected by micromanipulation individually. After primer extension preamplification (PEP) of the entire genome from each single NRBC, short tandem repeat (STR) genotype was analyzed after further amplification of this gene. Single NRBC was tested individually to identify if it was fetal or maternal in origin by STR genotype of NRBC and its corresponding parents. beta-globin DNA fragments were amplified with nested-PCR using PEP product of a single fetal NRBC that was determined to be fetal in origin. Fetal beta-globin genotypes were analyzed by reverse dot-blot hybridization (RDB), the accuracy was evaluated by comparing with genotype which had been determined on DNA obtained from chorionic villus (CVS) or amniocytes., Results: A total of 298 NRBCs were found in all of 28 pregnant women at a range of 4 to 13 per 5 ml venous blood. After PEP, about 43.6% of NRBCs were determined to be fetal in origin by STR typing. Using PEP product of a single fetal NRBC as template, beta-globin DNA fragment was examined on agarose gel after nested-PCR, amplification efficiency was 90.8% (118/130). Fetal beta-globin genotypes were achieved successfully in all cases with RDB. Comparing with the genotypes which were obtained from CVS or amniocytes, the rate of diagnostic accuracy was 85.7% (24/28)., Conclusions: PEP technique and STR genotype analysis provide effective method for identification of single nucleated erythrocyte from maternal blood in origin. With the techniques PEP and RDB, fetal beta-globin genetic diagnosis was achieved using a single fetal NRBC from maternal blood. The method had a high accuracy and reliability in diagnosis. It may become an optional approach to non-invasive prenatal diagnosis of beta-thalassemia.

Objective: To develop a method for identifying fetal nucleated erythrocytes (NRBCs) in maternal blood., Methods: NRBCs in maternal blood were detected by benzidine staining and collected by micromanipulation. After primer extension preamplification (PEP) of the entire genome from a single NRBC, short tandem repeat (STR) genotype was analysed after further amplification of this gene. Single NRBC was differentiated as fetal or maternal origin by comparison of STR genotype of NRBC with its corresponding parents., Results: NRBCs were found in all of 28 pregnant women in a range of 4 to 13 per 5 ml venous blood. About 43. 6% of NRBCs were determined to be fetal origin by STR typing., Conclusion: This method provides effective identification of fetal NRBCs and allows non-invasive prenatal genetic diagnosis using single fetal NRBC.