Application of quantitative fluorescent-polymerase chain reaction (QF-PCR) technique in the rapid prenatal diagnosis of down syndrome

The most frequent indication for prenatal diagnosis is the risk of increased trisomy 21 in fetus. In this study, it is targeted to show that the clinical practicability of QF-PCR technique in the rapid diagnosis of trisomy 21. Also, with this technique, the minumum required number of cells in order to diagnose trisomy and the number of amniocytes in relation to the gestational week were interpreted. In 224 pregnant women's amniotic fluid cell counts were carried out and the findings were classified according to gestational week. It was proved that there is a statiscally significant (p<0.001) relation between the total and viable cell number and viable cell ratio in amniotic fluid with the gestational week. The DNA isolation was made from 135 case. The DNA samples were amplified by using the D21S1411 locus on chromosome 21. It was calculated that the average peak ratio of normal samples is 1,1 and the peak ratio of trisomic diallelic samples is 2,0. It is demonstrated that the amniocyte number which is obtained from 0,1?1,9 ml amniotic fluid between the range of 14?22 gestation weeks is sufficient to diagnose by QF-PCR within an acceptable certainty range. It is calculated that the sensitivity of QF-PCR test is %90, specificity is %93,6, positive and negative predictive values are %100 in diagnosing trisomy 21. It is indicated that the heterozygosity ratio of D21S1411 marker is 0,8320. Based on these data, it is concluded that D21S1411 marker can safely be applied in Turkish population for diagnosis of trisomy 21. Key Words: Trisomy 21, QF-PCR, prenatal diagnosis, amniocyte.