Prenatal Diagnosis Of Edwards Syndrome By Quantitative Fluorescent Polymerase Chain Reaction With Short Tandem Repeats: D18S53, D18S59 And D18S488

ObjectiveTo investigate the feasibility and reliability of applying quantitative fluorescent polymerase chain reaction with short tandem repeats:D18S53, D18S59 and D18S488 located on chromosome 18 to detect of Edwards syndrome, based on this, develop a rapid, simple and accurate prenatal diagnosis technique for Edwards syndrome in clinic.Methods447 DNA samples were extracted from amniotic fluid and chorionic villus of unrelated individuals in Tianjin region, and then amplified with three short tandem repeats by QF-PCR,which including D18S53, D18S59 and D18S488. The amplification products were detected by ABI PRISM 377 sequence electrophoresis and analyzed using the GeneScan software. The data from GeneScan software of 378 amniotic fluid and 69 chorionic villus samples with normal karyotype were analyzed using the PowerStatsV 12 software. And genetical analysis was performed to conclude the data of population genetics such as the frequency of the alleles, heterozygosity of observation, the polymorphism information content, the discrimination power, and the probability of exclusion. The frequencies of the genotypes were tested with Hardy-Weinberg equilibrium. The results of 447 samples were compared with the ones of karyotyping.Specificity and sensibility were calculated using D18S53, D18S59 and D18S488 for prenatal diagnosis of Edwards syndrome.Result1.The frequencies of the genotypes of D18S53. D18S59 and D18S488 loci were consistent with the Hardy-Weinberg equilibrium.2. The results of karyotyping were as follow:438 cases were normal karyotype,8 cases were trisomy 18 and 1 case was triploid. Compared the results of 447 samples with karyotyping, the sensibilities using D18S53, D18S59 and D18S488 were 77.78%(7/9),44.44%(4/9),55.56%(5/9), respectively, and the specificities all were 100%.Using D18S53, D18S59 and D18S488,438 cases were diagnosed as normal and 9 cases were trisomy 18,and there were no false positive and false negative.The combied sensibility and specificity both were 100%.All of the samples received a report in 24-48 hours.3. When the samples with normal karyotype showed two peaks, the peak area ratio was 0.50-1.76,x+s=1.06±0.21, and 95 percent of the reference range was 0.65<peak area ratio≤1.47.The peak area ratio of two peaks with trisomy was 1.76-2.01, x+s=1.86±0.09, and 95 percent of the reference range was 1.68≤peak area ratio<2.03.The peak area ratio of trisomy with three peaks were about 1:1:1.Conclusion1.The genotypes distributions of D18S53, D18S59 and D18S488 loci were in accord with Hardy-Weinberg equilibrium. And the three STR were properly for gene diagnosis and prenatal gene diagnosis of Edwards syndrome.2. The sensibilities using D18S53,D18S59 and D18S488 were 77.78%(7/9), 44.44%(4/9),55.56%(5/9),respectively,and the specificities all were 100%.Using D18S53, D18S59 and D18S488, the combied sensibility and specificity both were 100%.3. When the samples with normal karyotype showed two peaks,95 percent of the reference range of peak area ratio were 0.65<peak area ratio≤1.47, and the trisomy were 1.68≤peak area ratio<2.03. The peak area ratio of trisomy with three peaks were about 1:1:1.4. QF-PCR was reliable for prenatal gene diagnosis of Edwards syndrome rapidly, simply and accurately. This method had high clinical values with it's high sensibility and specificity.