Prenatal diagnosis of Down syndrome using cell-free fetal DNA in amniotic fluid by quantitative fluorescent polymersase chain reaction.
BACKGROUND
Amniotic fluid (AF) supernatant contains cell-free fetal DNA (cffDNA) fragments. This study attempted to take advantage of cffDNA as a new material for prenatal diagnosis, which could be combined with simple quantitative fluorescent polymerase chain reaction (QF-PCR) to provide an ancillary method for the prenatal diagnosis of trisomy 21 syndrome.


METHODS
AF supernatant samples were obtained from 27 women carrying euploid fetuses and 28 women carrying aneuploid fetuses with known cytogenetic karyotypes. Peripheral blood samples of the parents were collected at the same time. Short tandem repeat (STR) fragments on chromosome 21 were amplified by QF-PCR. Fetal condition and the parental source of the extra chromosome could be determined by the STR peaks.


RESULTS
The sensitivity of the assay for the aneuploid was 93% (26/28; confidence interval, CI: 77%-98%) and the specificity was 100% (26/26; CI: 88%-100%). The determination rate of the origin of the extra chromosome was 69%. The sensitivity and the specificity of the assay in the euploid were 100% (27/27).


CONCLUSIONS
Trisomy 21 can be prenatally diagnosed by the QF-PCR method in AF supernatant. This karyotype analysis method greatly reduces the requirement for the specimen size. It will be a benefit for early amniocentesis and could avoid pregnancy complications. The method may become an ancillary method for prenatal diagnosis of trisomy 21.
Department of Medical Genetics, Peking University Health Science Center, Beijing 100191, China.
Dan
D
Wu
Reproductive Medicine Center, Peking University Third Hospital, Beijing 100191, China.
Hongbin
H
Chi
Reproductive Medicine Center, Peking University Third Hospital, Beijing 100191, China.
Minjie
M
Shao
Department of Medical Genetics, Peking University Health Science Center, Beijing 100191, China.
Yao
Y
Wu
Reproductive Medicine Center, Peking University Third Hospital, Beijing 100191, China.
Hongyan
H
Jin
Department of Medical Genetics, Peking University Health Science Center, Beijing 100191, China.
Baiyan
B
Wu
Reproductive Medicine Center, Peking University Third Hospital, Beijing 100191, China. Email: jie.qiao@263.net.
Jie
J
Qiao
D000653:Amniotic Fluid / Q000378:metabolism*; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics; D004314:Down Syndrome / Q000175:diagnosis* / Q000235:genetics*; D005260:Female; D006801:Humans; D018895:Microsatellite Repeats / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods*; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*