Relative deoxyribonucleic acid content of interphase leukocytes by flow cytometry: a method for indirect diagnosis of chromosomal abnormalities with potential for prenatal diagnosis.

A major goal of prenatal cytogenetic analysis is the development of minimally invasive techniques by which all pregnancies may be screened. That nucleated fetal cells exist in the maternal circulation raises the possibility that their cytogenetic status could be determined. However, these cells may not respond to commonly used mitogens. Thus it will probably be necessary to develop methods to analyze nondividing (interphase) cells. We therefore evaluated the use of flow cytometry as a means of determining whether the relative deoxyribonucleic acid content of G0-G1 leukocytes (expressed as the deoxyribonucleic acid index) could be used to verify aneuploidy or other chromosomal abnormalities. Our findings indicate this is indeed possible. We determined that the mean deoxyribonucleic acid index of circulating leukocytes from normal adult men (n = 15) was significantly different from that of leukocytes from normal adult women (n = 15). Similar results were obtained in leukocytes from umbilical cord blood of normal male neonates (n = 15) and normal female neonates (n = 15). Most importantly, values for leukocytes from each of 13 aneuploid individuals fell outside the range of values for leukocytes from normal adults of the same sex.