Determining fetal sex noninvasively is dependent of a robust assay. We designed a novel SRY assay and combined it with a SRY assay from literature forming a duplex assay with the same fluorescent dye to increase detection of Y-chromosome at low cell-free fetal DNA or chimeric DNA concentrations.
We analyzed 48 plasma samples from pregnant women in gestational weeks 5-35. Fetal sex was determined by DYS14 and SRY. We also compared 2 monoplex SRY assays with a SRY duplex assay at low DNA concentrations.
The DYS14 assay was more sensitive than the SRY assay, but less specific at low cell-free fetal DNA concentrations. We obtained a more sensitive duplex SRY assay with the same specificity as the 2 monoplex assays.
The SRY duplex assay improves the SRY detection at low DNA concentration.