Clinical Practice Of Genetic Testing For Hearing Loss

As the results of the national epidemiological for deafness show,hereditary hearing loss is extremely heterogeneous.Most of non-syndromic hereditary hearing losses,nevertheless,are found out to result from mutations of few genes.This fact grounds the establishment of genetic testing and prenatal diagnosis for hearing loss in China.Our study is dedicated to standardize and normalize the contents and processes of genetic testing,consulting and prenatal diagnosis,to make the accomplishment of human genome project widely available in diagnosis for deafness and reduction of deaf baby,and to eventually promote genetic testing,consulting and prenatal diagnosis in China.Partâ… Clinical Application of Genetic Testing and Consulting for Deafness in ChinaChapterâ… :Normalized Establishment of Clinical Genetic Testing Laboratory for DeafnessClinical genetic testing laboratory is the basis of genetic testing for deafness,the roles of which are to provide consumers clinical genetic testing and consulting.In China, there is no corresponding certification administration or rule,therefore,it is reasonable and efficient to set up genetic testing lab of our own norm according to foreign counterpart and Chinese rules for clinical PCR amplification genetic lab,which will make genetic testing for deafness develop well in China.Our study aim to normalize establishment of clinical genetic testing lab in three aspects:hardware(place and equipment),software(personnel and service),and quality contral.Chapterâ…¡:Clinical Genetic Testing for Non-Syndromie Hearing LossSince 2002,PLA genetic testing center for deafness has begun the clinical practice of common genetic testing for deafness.There have been 3202 probands receiving genetic testing by Apr.20^th2008.Our study summarizes and analyzes the results of the clinical practice.We put emphosis on the establishment of standard protocol,testing strategy and methods in the study,in addition to the analysis of the positive ratio of GJB2,SLC26A4,mtDNA 1494/1555 in groups of different phenotypes, analysis of genotype,phenotype and its relationship of GJB2 and SLC26A4,drawing the audiograms of GJB2 and SLC26A4 related hearing impairment.Finally,some practical problems that we may come into in genetic testing are discussed.Chapterâ…¢:Genetic Testing and Prenatal Diagnosis for Non-Syndromic Hearing LossGenetic counseling based on accurate genetic testing is very important in genetic service.Prenatal diangnosis can prevent hereditary hearing loss fundamentally,and eventually realize the aim of reducing hearing defect birth rate.During the practice of genetic counseling for more than 3000 counselors and 37 times prenatal diagnosis for 34 families,we have set up normalized protocols and contents of genetice counseling and prenatal diagnosis based on genetic testing for non-syndromic sensorioneural hearing loss,and discussed the importance of informed consent in clinical practice of genetic services.Chapterâ…£:Establishment of Laboratory Information Management System (LIMS)of Clinical Genetic Testing for DeafnessTo cater to requirement of informationization and networking of modem medicine, together with Rilintech IT Corporation,we have exploited the first set of laboratory information management system(LIMS)based on B/S database mode and a software platform composed of Linux,Apache,PHP,PostgreSQL.This system appear to function-rich,safe,stable,cheap,and easy to maintain,manipulate and expand,which primarily realize the aim of high performance and accuracy of information management, meanwhile,it has a great potentiality of exchanging information between multi-centers, and connection with electric equipment and HIS.(Hospital Information System).Partâ…¡Application of DNA Microarray in Clinical Genetic Testing for DeafnessChapterâ… :Feasibility Investigation of DNA Microarray Applied in Clinical Genetic Testing for DeafnessTo investigate the feasibility of a DNA microarray,designed according to the genetic background of China,in rapid genetic diagnosis of non-syndromic sensorineural heating loss(NSHL),we extracted genomic DNA samples from peripheral blood of 158 moderate to profound NSHL patients,and detected them with the DNA microarray which is able to perform mutation detection of 9 hot-spot mutations in four most common pathologic genes,including GJB2(35delG,176del16bp,235delC and 299₃00delAT),GJB3(538C＞T and 547G＞A),SLC26A4(IVS7-2,2168A＞G)and mitochondrial 12S rRNA(A1555G)simultaneously.At the same time,the results were confirmed with the traditional methods of sequencing and restriction fragment length polymorphism.Of 158 patients,67 were found out to be carriers of less than one pathogenic gene mutation.Among them,5(3.16%)have A1555G mutations,39 (24.68%)have GJB2 mutations(235delC homozygous mutation 24 cases,235delC and 299₃00delAT compound heterozygous mutation 7 cases,235delC heterozygous mutation 5 cases,299₃00delAT heterozygous mutation 2 cases,35delG heterozygous mutation 1 case),22(13.92%)have SLC26A4 gene mutations(IVS7-2 A＞G homozygous mutation 5 cases,IVS7-2 A＞G and 2168A＞G compound heterozygous mutation 5 cases,IVS7-2 heterozygous mutation 11 cases,2168A＞G heterozygous mutation 1 cases),and a patient has 299₃00delAT and IVS7-2 A＞G double heterozygous mutation in addition.No one carries GJB3 mutation.Except that two homozygous 235delC mutation cases were misjudged to be heterozygous mutation,the detection results of patients with microarray are identical to those with traditional methods,of which the positive ratio is 44.3%(70 cases).We jump to the following conclusion:being different from those traditional methods,the genetic diagnostic kit of hereditary deafness based on DNA microarray appears to have some inherent advantages in genetic diagnosis of NSHL,such as low time and money consuming,high performance and accuracy,which make it fit to be used in clinic practice.In addition,its features of easy manipulation,standardization and popularization endue it perfect prospect in clinical application.Chapterâ…¡:Clinical Application of DNA Microarray in Rapid Genetic Testing of Non-Syndromic Hearing LossTo increase the positive detection rate,and reduce the cost,the former DNA microarray were adjusted:167delT and 707T＞C were removed from the microarray slide,and mitochondrial DNA 1494C＞T was added on the slide.The adjusted DNA microarray then was applied in rapid genetic testing of NSHI.Results show that 76%EVAS could be detected positively by DNA microarray, while 95%by sequencing,with a significant difference(p=0.000),which suggests that sequencing cannot be taken the place by microarray in genetic testing of the EVAS patients.DNA microarry should be combined with sequencing to set up the platform of genetic testing for deafness,which could take advantage of both rapid,economic, high-performance features of mircroarray and high accuracy and positive detection rate features of sequencing.In the discuss part,we analyze how to clinically hereditarily explain the different results we obtain in utility of DNA microarray,overlook the future of DNA microarray for genetic testing for deafness in three aspects:increasing detected mutation points,minimizing the microarry system,and improving marking technique, and evaluation social and economic benefit of deafness prevention system based on the combination of genomic accomplishment for deafness and nanomicroarray technique.Partâ…¢Promotion and Popularization of Clinical Genetic Testing for DeafnessTo make clinical genetic testing easily available for more health care providers, the affected and their relatives,we have put emphasis on promotion and popularization through various methods and ways,including propagandizing in clinics and wards, launching nationwide class of genetic testing for deafness,providing testing freely and giving lectures in local schools for the deaf,setting up the first website and blog about genetic testing for deafness,cooperating with the largest deaf community, www.cndeafcom,on internet,and so on.More and more health care givers,the deaf have received knowledge about genetic testing and taken much interest in,and then utilize this molecularly testing tool.