Genotype And MCV And MCH Analysis Of 3234 Thalassemia Samples In Hunan

ObjectiveTo analyze the mutation spectrum of thalassemia genes and the distribution characteristics of MCV and MCH of different genotypes in Hunan,to compare the energy efficiency of screening for thalassemia by three international and domestic commonly used MCV and MCH cut-off values,and to provide reference for the development of suitable screening programs for thalassemia in the region.MethodsThe MCV and MCH were detected by fully automated blood cell analyzer,three common deletion typeα-thalassemia mutations were detected by Gap-PCR,three commonα-thalassemia point mutations and17 common β-thalassemia point mutations were detected by RDB-PCR,and the data of positive genetic test samples were collected and analyzed by SPSS26.0 statistical software.Results1.Among the 3234 positive samples for thalassemia,56.83%,41%and 2.16%were for a, βand a/ βcombined thalassemia,respectively.α-thalassemia was most common with-^SEA/ααgenotype,followed by-α^3.7/ααand-α^4.2/αα,and the top three for β-thalassemia were IVS-II-654M/N,CD41-42M/N and CD17M/N,in order of prevalence.The percentage of the most common cases was similar to that of some surrounding areas,and differed greatly from that of Yunnan,Guangxi and Hainan.2.The blood routine MCV and MCH values gradually decreased with the aggravation of the clinical typing of thalassemia;the average values of MCV and MCH of the silent thalassemia were all within the normal range;the majority of the mild thalassemia,a/ β compound thalassemia and all the intermediate thalassemia MCV and MCH values were below the normal range;the average values of MCV and MCH of the mild thalassemiaα^CSα/ααand CAPM/N types were still within the normal range.The mean values of MCV and MCH of β^EM/N of mild thalassemia were near the lower limit of detection of normal range;a/ β compound thalassemia showed mostly β-thalassemia characteristics,and CAPM/N compound other mutation types showed only the characteristics of other mutations.3.There was no statistical difference in the energy efficiency of the three commonly used MCV and MCH cut-off values for the screening of thalassemia;the missed diagnosis rates of the three cut-off values for a, βand a/ βcombined thalassemia were 28.84%-30.52%,4.52%-5.28%and 5.71%-8.57%,respectively;the three cut-off values had no missed diagnosis for intermediate thalassemia and some mild thalassemia;the missed diagnosis rates for silentα-thalassemia and mild thalassemia were as high as 59.69%-80.93%and about 1%for mildα-thalassemia---^SEA/αα;and 100%,35%-52.5%for mild β-thalassemia CAPM/N and β^EM/N,respectively,and 2.27-4.53%for other mild β-thalassemia.4.The total proportion of the four mutations-α^3.7,-α^4.2,α^CSαand β^E,which are easily missed in the initial screening of MCV and MCH and may lead to the risk of birth of children with moderate to severe thalassemia,ranged from 13-62%in 10 southern provinces,and 28.33%in Hunan Province,among which the proportion of the twoα^CSαand β^Emutations,which can lead to abnormal hemoglobin production,also differed significantly among provinces.Conclusion1.The mutation spectrum of thalassemia genes in Hunan is similar to that of most neighboring provinces,and differs from that of Guangxi,Yunnan and Hainan.2.The MCV and MCH values of different genotypes of thalassemia varied,and the MCV and MCH values of silent thalassemia and the 2types of mild thalassemia,α^CSα/ααand CAPM/N,were still in the normal range.3.There was no statistical difference in the screening effect of the three commonly used MCV and MCH cut-off values for thalassemia,and there was a high rate of missed detection for the silent thalassemia and the three types of mild thalassemia,α^CSα/αα,CAPM/N,and β^EM/N.4.Simultaneous screening of MCV and MCH in couples can improve the detection rate of individuals with single mutations of-α^3.7,-α^4.2,α^CSαand β^E,whose spouses are homozygous for the same type of thalassemia,and enhance the screening efficiency of the primary screening test.In practice,different screening procedures such as routine blood screening for both spouses or routine blood screening for the female partner combined with hemoglobin electrophoresis should be used flexibly according to the patient’s consultation mode（both spouses/only the female partner）and household origin.