diagnostic value of real time quantitative pcr for prenatal detection of down syndrome in amniocyte samples obtained from high risk pregnancies

downs syndrome (ds) is one of the most common chromosomal abnormalities (1 in 700-1000 births) and one of the main causes of mental retardation. therefore, diagnosis and prevention of live-born children with ds is a principle priority for the iranian ministry of health. this study was performed to evaluate the application of real-time qpcr technique for rapid diagnosis of ds. about 15-20 milliliter of the amniotic fluid was taken under sterile conditions. about 12 to 15 ml of each sample was used for cytogenetic analysis and the rest was used for dna extraction. then, quality and quantity of dna was measured. dyrk1a, dscam and pmp22 genes were analyzed as target and reference genes, respectively. specific primers were designed by primer express software. real-time qpcr assay was done using serial dilutions to make a standard curve. subsequently, the reaction for all samples was performed and gene dosage was calculated using 2–δδct formula. the results of real-time qpcr showed the target/reference genes ratio in ds and normal fetus samples was 1.61 ± 0.09 and 1.03 ± 0.05, respectively. this demonstrated the presence of three copies of target genes in ds and two copies in normal fetus samples. the results of real-time qpcr were confirmed by cytogenetic analysis. nowadays, the methods which are based on cytogenetic analysis such as karyotyping and fish are used as standard techniques to detect patient individuals as well as prenatal diagnosis. these methods are generally too time-consuming, expensive for clinical applications and also need cultured live cells. in contrast, real-time qpcr as a molecular technique is a high throughput technique with none of the above mentioned limitations. therefore, based on these results, real-time qpcr technique can be used for rapid prenatal diagnosis of ds as an accurate, sensitive and reliable technique.