This problem is particularly acute in sickle cell disease, in which HbC, HbS, and rs713040 are all within 12 bp of each other; and the HBD gene is a close paralog of HBB. These factors might have contributed to the 80% accuracy obtained in a previous study that used dPCR for NIPT of sickle cell disease42. This evidence concerns the gene HBD and sickle cell disease.