Rapid detection of trisomy 21 by gene dosage analysis using quantitative real-time polymerase chain reaction.
OBJECTIVE
Rapid detection of fetal aneuploidy helps inform a mother's choice about the course of her pregnancy. Obtaining results by fluorescent in situ hybridization (FISH) requires more than 24 h, and thus a more rapid method is needed.


METHODS
Conventional G-banding and FISH for chromosome 21 were performed for cultured amniocytes. Genomic DNA was extracted from uncultured amniocytes obtained from 23 patients. TaqMan polymerase chain reaction (PCR) primers were designed to amplify the potassium voltage gated channel gene on chromosome 21q22.12 and the ribosomal phosphoprotein gene on 18q21.1. Quantitative real-time PCR was performed for these two gene fragments and the differences of the threshold cycle (Ct) of the two genes (Ct 18-Ct 21) were calculated for each sample.


RESULTS
G-banding revealed that 19 patients had a normal karyotype and four had trisomy 21. FISH resulted in one case of a false positive. The Delta Ct values (Ct 18-Ct 21) of trisomy 21 patients were significantly higher than the values of individuals with normal karyotypes (P < 0.001) and there was no overlapping.


CONCLUSIONS
Fetal trisomy 21 is rapidly detectable by gene dosage analysis from amniocytes using quantitative real-time PCR.
Tsujie
Tomoko
T
Division of Obstetrics and Gynecology, Department of Specific Organ Regulation, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Takemura
Masahiko
M
Kimura
Tadashi
T
Shimoya
Koichiro
K
Tsutsui
Tateki
T
Ogita
Kazuhide
K
Ozaki
Mamoru
M
Murata
Yuji
Y
D000653:Amniotic Fluid / Q000502:physiology; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D018628:Gene Dosage; D006801:Humans; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*
D004247:DNA