Y chromosome-specific sequences can be used to detect remaining male cells after sex-mismatched allogeneic blood stem cell transplantation (HSCT) involving a male patient and female donor, which represents approximately 25% of all cases. We developed a quantitative Y chromosome-specific PCR assay (QYCS-PCR) based on the DFFRY gene for the determination of hematopoietic donor chimerism. We analyzed blood and marrow samples from more than 40 patients at various time points after both standard and nonmyeloablative allogeneic HSCT. We found that real-time PCR combines extreme sensitivity, with a detection level of less than 1 male in 100,000 female cells (
