Gene Detection Of Thalassemia In Guangdong Area

Background:Thalassemia was first described by Cooley and Lee in 1925,It was first discovered in the Mediterranean,so it is called thalassemia,also known as maritime anemia or globin-forming anemia.About 2%of the population in the world are carriers of the thalassemia gene.The disease is highly prevalent in Southern of China,The carrying rates of the population in Guangxi and Guangdong were about23.98%?reported in 2010?and 11.07%?reported in 2004?respectively.Thalassemia is a hematological disease that is a serious threat to human health.it is inherited by autosomal recessive model and can be classified into?-thalassemia,?-thalassemia,?-thalassemia,?-thalassemia,??-thalassemia and????-thalassemia according to the decrease of peptide chain synthesis,?-thalassemia and?-thalassemia are the most common thalassemia.Clinically,thalassemia can be divided into mild?thalassemia gene carriers?,intermediate and severe according to anemia status.Carriers of mild thalassemia exhibit mild hypochromic microcytic anemia,intermediate patients have obvious anemia symptoms and require irregular blood transfusions,and severe thalassemia patients develop edematous fetuses??-thalassemia?or developmental jaundice,hepatosplenomegaly,without treatment,the child will die before the age of5??-thalassemia?.The diseasing causing gene of thalassemia is human globin gene,In the late 1970s,the?-globin gene and?-globin gene were successively located,and it was subsequently found that the human globin gene exists in the form of a gene cluster,and the?-globin gene cluster was located at 16p13.3 and the?-globin gene cluster was located at 11p15.5.Adult?-globin is mainly encoded by?1 and?2 genes?i.e.HBA1 and HBA2?,and?-globin is mainly encoded by?gene?i.e.HBB gene?.So far,there is no effective treatment for thalassemia,among which the promising treatments are gene therapy and bone marrow stem cell transplantation.However,the basic measure for prevention and treatment is to do primary prevention,that is,to screen the thalassemia gene for both couples,and to conduct prenatal diagnosis for the fetus that may carry thalassemia to prevent the birth of the child.At present,the genetic testing for thalassemia is to do screening first,which when the blood routine results meets Hb<110 g/L,MCH<27 pg,MCV<80 fl,hemoglobin electrophoresis should be done;when abnormal hemoglobin and abnormal Hb A2 level is detected,a conventional genetic diagnosis is performed.Therefore,it is very necessary to conduct in-depth research on this disease and increase the detection of rare thalassemia,especially when traditional testing cause missed diagnosis of partially static thalassemia.Objectives:First of all,with the development of the national economy,the intensification of population mobility and the reform of the marriage and childbearing system,the previously reported data of thalassemia in Guangdong Province has no practical reference value.therefore,the re-examination of thalassemia carriers in Guangdong in recent years is of great significance for the clinical detection,treatment and disease control of thalassemia in this area.Secondly,in view of the fact that there are many missed diagnosis caused by clinical detection in resting thalassemia,it is of great practical significance to establish a set of accurate,simple and clinically feasible detection standard scheme.Third,through the screening of thalassemia,we can find rare types of thalassemia families,follow up and treat them,and enrich the epidemiological data of thalassemia.it will provide an important reference for more accurate diagnosis,treatment and prenatal diagnosis of patients with thalassemia in Guangdong in the future.Methods:The study subjects were from couples,proband children and fetuses who underwent thalassemia tests at the Reproductive Medicine Center and Prenatal Diagnostics Department of The third affiliated Hospital of Guangzhou Medical University from January 1,2014 to August 31,2019,The Reproductive Medicine Center conducts a full thalassemia screening for all the patients,a total of 30072 cases of thalassemia genetic testing and 2795 prenatal diagnosis of the fetus.All samples were subjected to thalassemia screening?routine blood tests,hemoglobin electrophoresis?and genetic gene detection,when abnormal hemoglobin or hemoglobin A2?HbA2?content is detected,genotyping and diagnosis can be performed by cross-breakpoint PCR?Gap-PCR?,reverse dot hybridization?RDB-PCR?and sequencing.For those routine method detected negative with abnormal screening result,rare thalassemia mutation type should to detected further.In order to prevent the birth of moderate-severe fetuses caused by missed diagnosis,the Department of Reproductive Medicine of our hospital will arrange for the patient to do the above-mentioned detection of thalassemia gene.For those who need to check the genotype of fetal thalassemia,amniocentesis is performed for pregnant women during the second trimester of pregnancy,the above method was used to diagnose the DNA of the cultured amniotic fluid cells.Results:In this study,through the gene detection of thalassemia in 30072 blood samples and 2795 prenatal samples,for peripheral blood samples,5945 cases were detected as thalassemia,the positive rate is 19.77%;the total positive rate of?-thalassemia is15.14%with 4554 cases,and the positive rate of?-thalassemia is 3.99%with 1199cases,and the positive rate of?combine?thalassemia is 0.64%with 192 cases.1.the distribution of common?-thalassemia:for peripheral blood samples,we detected 1523 cases of static type?33.81%?,2807 cases of mild type?62.31%?,174cases of intermediate type?3.86%?and 1 case of severe type?0.02%?;for prenatal diagnosis samples,there were 405 cases of static type?21.57%?,971 cases of mild type?51.70%?,138 cases of intermediate type?7.35%?and 364 cases of severe type?19.38%?.2.The distribution of common?-thalassemia:for peripheral blood samples,we detected 1110 cases of mild type?96.77%?,22 cases of intermediate type?1.92%?and15 cases of severe type?1.31%?;and for prenatal diagnosis samples,there were 721cases were mild type?72.32%?,27 cases were intermediate type?2.71%?and 249cases were severe type?24.97%?.3.For common?combined with?thalassemia,for peripheral blood samples,192cases were detected,static?-thalassemia with?⁺/?^N is 13.02%with 25 cases,static?-thalassemia with?⁰/?^N is 29.69%with 57 cases,mild?-thalassemia with?⁺/?^N is13.54%with 26 cases,mild?-thalassemia with?⁰/?^N is 43.75%with 84 cases;for prenatal diagnosis samples,142 cases were detected,static?-thalassemia with?⁺/?^N is4.93%with 7 cases,static?-thalassemia with?⁰/?^N is 27.47%with 39 cases,mild?-thalassemia with?⁺/?^N is 14.79%with 21 cases,mild?-thalassemia with?⁰/?^N is45.07%with 64 cases,hemoglobin H with?thalassemia is 4.23%with 6 cases,Bart's fetal with?thalassemia is 1.41%with 2 cases,and?-thalassemia with moderate to severe?thalassemia is 2.11%with 3 cases.4.For rare type of?and?thalassemia,for peripheral blood samples,48 cases of?-thalassemia?4 cases of deletion,44 cases of non-deletion?and 52 cases of?-thalassemia?8 cases of deletion,44 cases of non-deletion?were detected;for prenatal diagnosis samples,1 case of?-thalassemia deletion was detected.Conclusions:First,this study carried out a large sample screening and diagnosis of thalassemia in Guangdong in the past five years,which enriched the epidemiological characteristics of thalassemia in this area.the main findings of this study are as follows:1.the mutation carrying rate of?-thalassemia is higher than that of?-thalassemia in Guangdong population;2.The proportion of mutation types is also consistent with the mutation frequency characteristics of southern Chinese population.The main types of?-thalassemia are SEA deletion type in Southeast Asia(--^SEA/??),3.7kb right deletion type(-?^3.7/??)and 4.2 kb left deletion type(-?^4.2/??).The most common mutation types of?-thalassemia in this study were?^CD41-42/?N,?^IVS-II-654/?^N,?^-28/?^N and?^CD17/?^N.The rare type of?-thalassemia is mainly IVS-II-55 and???^HK.The most common mutation types of rare type?-thalassemia in this study are:Hb New York and CD22.In this study,the combination of thalassemia screening and conventional gene diagnosis optimized the detection process of clinical thalassemia and greatly improved the detection rate of static thalassemia and rare pedigrees.it provides a reference basis for the development of new testing methods in clinical examination in the future.In a word,the results of this study can provide an important reference for clinical diagnosis and treatment,prenatal diagnosis or reproductive genetic counseling of patients with thalassemia in Guangdong.