ABSTRACT
OBJECTIVE: Trisomy 21 (Down syndrome) is the most common chromosomal anomaly which occurs 1 out of 700-1000 birth. Current techniques such as amniocentesis, chorionic villi sampling (CVS), require lengthy laboratory culture procedures and high costs. This study was undertaken to establish a rapid prenatal diagnosis of trisomy 21 using real-time quantitative polymerase chain reaction of fetal DNA from amniotic fluid. METHODS: Real-time quantitative PCR was performed with DNA template obtained from 14 normal serum, 10 normal amniotic fluid samples, 14 Down syndrome serum, and 7 Down syndrome amniotic fluid samples. Primers for D21S167 and S100B of chromosome 21 were used. Primers that direct amplification of 165-bp fragment of the IGFI (Insulin-like growth factor-1) gene on chromosome 12 are included to generate an internal standard for quantitation. RESULTS: The relative levels of D21S167 and S100B were 2.6 and 2.4 times higher in the serum of Down syndrome patients compared to the control group. The difference between these two groups was statistically significant (P-value: 0.0012 and 0.0016). The relative levels of D21S167 and S100B were 2.1 and 2.7 times higher in the amniotic fluid of Down syndrome fetuses compared to control group. The difference between these two groups was statistically significant (P-value 0.0379 respectively). CONCLUSION: Prenatal diagnosis of trisomy 21 by real-time quantitative PCR-associated STR (small tandem repeats) analysis of D21S167 and S100B is useful, accurate and rapid diagnostic method and also can be employed in diagnosis of trisomy 13, 18. Furthermore, it may also be useful for prenatal diagnosis with fetal DNA from maternal blood and for preimplantation genetic diagnosis.