Development of noninvasive prenatal diagnosis of trisomy 21 by RT-MLPA with a new set of SNP markers.

ABSTRACT

INTRODUCTION: Placental mRNA can now be detected in maternal whole blood, raising the possibility of using maternal blood for noninvasive prenatal diagnosis (NIPD) of trisomy 21. We aimed to identify new mRNA-single nucleotide polymorphism (mRNA-SNP) markers suitable for use in reverse-transcriptase multiplex ligation-dependent probe amplification (RT-MLPA) to develop a more reliable diagnostic method for trisomy 21 in Chinese subjects. MATERIALS AND METHODS: Using sequencing, we determined the status of SNPs in genes expressed in the placenta and calculated their heterozygote frequencies to determine which loci were suitable for use in RT-MLPA. Cell-free fetal RNA was extracted from peripheral blood samples of 246 women at 12-24 weeks of pregnancy, and the SNP loci selected were analyzed by RT-MLPA, followed by capillary electrophoresis. Karyotype analyses were used to confirm the diagnosis of trisomy 21. RESULTS: As compared with karyotype analysis, the diagnostic sensitivity and specificity of RT-MLPA were excellent (95 and 100% in different gestational weeks). CONCLUSION: The RT-MLPA technique is a suitable and reliable method for the diagnosis of trisomy 21. Use of RT-MLPA with the SNP markers described here shows good specificity, high sensitivity, and high throughput potential, making this technique suitable for NIPD in clinical practice.