Down Sendromunun Hızlı Doğum Öncesi Tanısında D21S1411 Kısa Tandem Tekrar (STR) Belirteci Kullanılarak Kantitatif Floresan Polimeraz Zincir Reaksiyonu (QF-PCR) Tekniğinin Etkinliğinin Değerlendirilmesi

Abstract

Giriş ve Amaç: Doğum öncesi tanı için en sık endikasyon, fetusda artmış trizomi 21 riskidir. Bu çalışmada, trizomi 21’in hızlı doğum öncesi tanısında QF-PCR tekniğinin klinik uygulanabilirliğinin gösterilmesi amaçlandı. Ayrıca, bu teknikle trizomi tanısı koyabilmek için gerekli en az hücre sayısı ve bu değerin gebelik haftalarıyla ilişkisi değerlendirildi. Olgular ve Yöntem: 224 gebeye ait amniyon sıvısında hücre sayımı yapıldı ve gebelik haftalarına göre sınıflandırıldı. Amniyon sıvısında bulunan total ve canlı hücre sayısı ile canlı hücre oranının gebelik haftasıyla istatistiksel olarak anlamlı bir ilişkisi olduğu (p<0.001) gösterildi. 135 olgudan DNA ayrımı yapıldı. DNA örnekleri D21S1411 belirleyici ile QF-PCR kullanılarak çoğaltıldı. Bulgular: Normal örneklerin pik oranı ortalama 1.1 ve trizomik diallelik örneklerin pik oranları 2.0 olarak hesaplandı. 14–22. gebelik haftaları arasında 0.1–1.9 ml amniyon sıvısından elde edilen amniyosit sayısının QF-PCR ile tanı koymak için yeterli olduğu gösterilmiştir. QF-PCR testinin trizomi 21’i teşhis etmede duyarlılığının %90, seçiciliğinin %93.6, pozitif ve negatif öngörü değerlerinin ise %100 olduğu hesaplanmıştır. D21S1411 belirleyicinin heterozigozite oranının ise 0.8320 olduğu gösterilmiştir. Sonuç ve Tartışma: D21S1411 belirleyicinin Türk toplumunda trizomi 21 tanısı için güvenle kullanılabileceği sonucuna varılmıştır. QF-PCR analizi, trizomi 21’in hızlı tanısında uygulanabilecek yardımcı bir testtir. Daha fazla sayıda belirleyici ile çalışmak, testin duyarlılığını artıracaktır.

Keywords

• Trizomi 21, QF-PCR, doğum öncesi tanı, amniyosit

EVALUATION OF EFFECTIVENESS OF QUANTITATIVE FLUORESCENT- POLYMERASE CHAIN REACTION (QF-PCR) TECHNIQUE USING D21S1411 SHORT TANDEM REPEAT (STR) MARKER IN THE RAPID PRENATAL DIAG

Abstract

Introduction: The most frequent indication for prenatal diagnosis is the increased risk of trisomy 21 in fetus. In this study, it is targeted to show the clinical practicability of QF-PCR technique in the rapid diagnosis of trisomy 21. Additionally, the minumum required number of cells in order to diagnose trisomy and the minumum number of amniocytes in relation to the gestational week were also evaluated with this technique.Material and Method: Amniotic fluid cell counts were carried out in 224 pregnant women and the findings were classified according to the gestational week. It was proved that there is a statistically significant (p<0.001) relationship between the total and viable cell number, viable cell ratio in amniotic fluid and the gestational week. The DNA isolation was made for 135 case. The DNA samples were amplified with using the determinant of D21S1411 locus on chromosome 21 by QF-PCR.Results: 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 was shown that amniocyte number obtained from 0.1–1.9 ml amniotic fluid of 14–22 gestational weeks woman is sufficient to diagnose trisomy by QF-PCR within an acceptable range of certainty. It was calculated that the sensitivity of QF-PCR test in diagnosing trisomy 21 was 90%, specificity was 93.6%, positive and negative predictive values were 100%. It was indicated that the heterozygosity rate of D21S1411 marker was 0.8320. Conclusion: It is concluded that D21S1411 marker can safely be applied in Turkish population for diagnosis of trisomy 21. QF-PCR analysis is a helping test that could be used for rapid prenatal diagnosis of trisomy 21. Studying with more number of markers will increase the sensitivity of the PCR test

Keywords

• Trisomy 21, QF-PCR, prenatal diagnosis, amniocyte

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