Study On Prenatal Diagnosis Of Aneuploidies By Fluorescence In Situ Hybridization

Objective To evaluate the feasibility and utility of using fluorescence in situ hybridization(FISH) for prenatal diagnosis of common chromosome aneuploidies.The aim of the study is to develop an accurate and rapid molecular genetic technique for common chromosome aneuploidies in clinic,so that can lower the morbidity of chromosome disease.Methods Amniocentesis was performed on 109 women at 20～25 weeks of pregnancy,which were high risk in serologic screening at prenatal diagnostic centre of the General Hospital of Tianjin Medical University.2～3mL uncultured amniotic fluid was detected by FISH using chromose-specific DNA probes of 13,18,21,X and Y chromosomes.15mL amniotic fluid was cultured for karyotype analysis at the same time.FISH results were compared to the results of karyotype analysis.Results(一)The results of karyotype analysis:109 cultured amniotic fluid cells were all successful in one time.6 abnormal karyotypes(3 of trisomy 21,2 of mosaic,the other one is 47,XX,+mar)and 103 normal karyotypes were detected by karyotype analysis.(二)The results of FISH:The results of judgement:(1)The first group of DNA probes,the normal diploid have 2 jacinth and 2 green signals in one cell;if there are 3 jacinth or 3 green in one cell,it demonstrates that is trisomy 21 or trisomy 13.(2)The second group of DNA probes,there is 1 jacinth signal,1 green signal and 2 azure signals in one cell of the normal male;and there are 2 green and 2 azure signals in one cell of the normal female;if there are 3 azure signals in one cell,it demonstrates that is trisomy 18.In addition,if the number of jacinth and green signal do not accord with the above mentioned,it demonstrates that is abnormal of sex chromosomes.There were 105 having results in the 109 samples.The achievement ratio was 96.3%.100 normal karyotypes and 5 aneuploidies(3 of trisomy 21 and 2 of mosaic)were detected by FISH.The 99 normal karyotypes of FISH were same as the karyotype analysis,but the chromosome karyotype of 47,XX,+mar was found by karyotype analysis in another case,whose FISH signal showed normal.The reason of fail to diagnose the 47,XX,+mar is that the origin of the marker chromosome is not the 13,18,21,X and Y chromosomes.The 5 aneuploidies of FISH were same as the karyotype analysis completely.In this study,The sensitivity,specificity and accuracy of FISH is 83.3%,100%and 99%respectively.But as for 13,18,21,X and Y chromosome-specific probes,the sensitivity,specificity and accuracy of FISH is 100%.Conclusion 1,FISH technique showed high sensibility,specific and stable results.2,FISH technique for prenatal diagnosis of the most common chromosome disorders(trisomies 21,13,18 and sex chromosome aneuploidies)where results are available within 24～48h.The procedure of FISH is easy to operate and the signals are easy to read.FISH also use less samples.This method has clinical values.