The value of plasma fetal free DNA in the screening of Down syndrome in pregnant women of advanced maternal age / 国际检验医学杂志

ABSTRACT

Objective To investigate the value of plasma fetal free DNA in the screening of Down syndrome in pregnant women of advanced maternal age .Methods 298 cases of pregnant women of advanced maternal age in our hospital from February 2012 to May 2014 were chosen as the research object ,who experienced prenatal serological screening and fetal free DNA detection by high-throughput gene sequencing technology .According to the karyotype analysis of amniotic fluid/umbilical cord blood puncture ,we compared the detection efficiency of traditional serological screening and high-throughput noninvasive DNA detection for prenatal Down's syndrome screening in pregnant women of advanced maternal age ,and evaluated their sensitivity and specificity .Results 26 cases of high risk pregnant women were screened by using serological methods (positive rate was 8 .7% ) .Among them ,we found 20 cases of high risk pregnant women with Down syndrome (21-trisomy) (Tang screening positive rate was 6 .7% ) ,and 5 cases of 18-trisomy syndrome (1 .7% ) and 2 cases of 13-trisomy syndrome(0 .7% ) .9 cases of high risk pregnant women (positive rate was 8 .7% ) was detected with noninvasive DNA technology ,all within the range of serological screening results (positive rate was 3% ) .Among them ,there were 6 cases of high risk 21-trisomy (positive rate was 2% ) ,and 3 cases of high risk 18-trisomy (1% ) . High risk pregnant women were further verified by amniotic fluid/umbilical cord blood cell karyotype analysis .The results showed that there were 5 cases of 21-trisomy positive(1 .7% ) ,2 cases of 18-trisomy positive(0 .7% ) ,and 2 cases were normal(0 .7% ) .The sensitivity ,specificity and accuracy of serological screening were 100% ,93 .3% and 94 .9% respectively .The sensitivity ,specificity and accuracy of noninvasive DNA detection were 100% ,97 .9% and 99 .6% respectively .There were statistically significant differ-ences on the total positive rate ,Tang screen positive rate ,Tang screening false positive rate ,specificity and positive predictive value between the two methods (P<0 .05) .Conclusion Analysis of cffDNA using noninvasive DNA detection technique has a high sen-sitivity ,specificity and accuracy for DS screening in elderly patients ,and deserves clinical promotion .