Study On Clinical Performance Of Method BACs-on-Beads

PurposeMethod BACs-on-Beads is a new method used in rapid prenatal diagnosis, through marking the locus of the target area, this method can be used to diagnose chromosome aneuploid abnormalities (13,18,21,X and Y chromosomes) and10types of micro-deletion syndrome through detecting the DNA samples extracted from human specimens (amniotic-fluid) with the designed probe. This study discusses the feasibility of this new detection method in clinical practice in a way of evaluating the accuracy, sensitivity and specificity and its prediction value in rapid prenatal diagnosis through comparing method BoBs with traditional method G banding karyotype analysis.MethodologyThis test is divided into two parts, both apply the self-paired design program.Part1(retrospective study):selecting20amniotic fluid specimens whose karyotype results have been determined from cytogenetic room selected from Peking union medical hospitals and1positive specimens from DNA cell lines(DiGeorge1syndrome), conduct verification tests on method BoBs, compare the test results of method BoBs with the known karyotype analysis results to verify the accuracy of method BoBs.Part2(prospective study):detect the aneuploid abnormalities and microdelection syndrome with method BoBs on pregnant women who receiving amniocentesis for prenatal diagnosis in Peking union medical hospitals from2011-10to2012-03, analyze the detection results through BoBsoft software. Compare the results of method BoBs and G banding karyotype analysis to evaluate the sensitivity, specificity and accuracy of this new method. Results1.In the retrospective part of this study, through detection of DNA samples extracted from amniotic fluid, we know that the concentration of3patients is lower than4ng/μl, therefore,18samples were detected in method BoBs, totally,1patient with disease Trisomy18syndrome,2patients with disease Trisomy21syndrome and1patient with disease DiGeorge1syndrome were discovered, this results are consistent with the known karyotype analysis results, thus the accuracy, specificity and sensitivity of method BoBs may be verified.2.In the prospective part of this test:①390DNA samples in total from fresh amniotic fluid were detected by using method BoBs, the test results were conducted with quality control evaluation and we found that377samples were tested to be qualified, the detection success rate of this method is96.7%(377/390). In the test,1patients with disease Trisomy18syndrome,7patients with disease Trisomy21syndrome and1patients with abnormal15chromosomes were diagnosed;②through comparison with analysis results of method G banding karyotype analysis used to detect samples, method BoBs totally missed2chromosomal abnormalities (including1with disease Trisomy18syndrome and1with chimera). One sample detected with chromosomal15abnormalities by using method BoBs were used to diagnose disease Trisomy21syndrome through method G banding karyotype analysis, after tested with method Array-CGH, it is verified that the detection results of method BoBs were correct (repeated teratogenicity of longer arm fragment of chromosome15);③through statistical analysis, it is showed that, compared with traditional method G banding karyotype analysis, the positive rate, sensitivity, false positive rate, specificity and accuracy of method BoBs are respectively2.4%;81.8%;0;100%and99.5%.Conclusion1.There is good correlation between method BoBs with traditional method G banding karyotype analysis;2.Method BoBs is a rapid, reliable and easily operated method to detect chromosome aneuploid abnormalities and microdeletion syndrome. 3.Method BoBs has high sensitivity, specificity and accuracy, it can be used to substitute FISH; QF-PCR and other rapid prenatal diagnosis methods.4.Combination of method BoBs and method G banding karyotype analysis can greatly improve the accuracy and diversity of prenatal diagnosis.S.This diagnostic method is not used for chimerism, this product that is not cover abnormal chromosomal regions of amplification and deletion, point mutation, balanced rearrangements (inverted and displacement), ploidy variation, uniparental disomy and methylation alterations.