PRENATAL-DIAGNOSIS WITH USE OF FETAL CELLS ISOLATED FROM MATERNAL BLOOD - 5-COLOR FLUORESCENT IN-SITU HYBRIDIZATION ANALYSIS ON FLOW-SORTEDCELLS FOR CHROMOSOME-X, CHROMOSOME-Y, CHROMOSOME-13, CHROMOSOME-18, AND CHROMOSOME-21

OBJECTIVE: Currently, prenatal diagnosis of chromosome abnormalities r equires invasive techniques such as amniocentesis and chorionic villus sampling that carry small but finite risks of fetal loss. A noninvasi ve approach is to isolate fetal cells from maternal blood by flow sort ing followed by genetic interphase analysis with fluorescence in situ hybridization. Because the ratio of fetal to maternal cells is relativ ely low after flow sorting and to detect 90% to 95% of fetal aneuploid ies associated with serious birth defects, a 5-color fluorescent in si tu hybridization strategy is necessary for simultaneous detection of c hromosomes X, Y, 13, 18, and 21 in all flow-sorted nuclei recovered fr om a specimen. STUDY DESIGN: Fetal nucleated red blood cells were isol ated from maternal blood in 40 cases (10.4 to 27.0 weeks' gestation) b y flow cytometry on the basis of positive selection of CD71(+) (transf errin receptor), CD45(-), and LDS751 staining. Each case was evaluated for 5-color fluorescent in situ hybridization efficiency by determini ng the percentage of flow-sorted nuclei containing 8 hybridization sig nals for chromosomes X, Y, 13, 18, and 21. RESULTS: A total of 42,312 flow-sorted nuclei from maternal blood samples were analyzed. In 5 of 16 (31%) cases with a male fetus, 0.16% of nuclei scored were identifi ed as fetal by the presence of I signal each for chromosomes X and Y. Fetal trisomy 21 nuclei were accurately detected in 2 cases with a fem ale fetus, each of which was subsequently confirmed. CONCLUSIONS: Five -color interphase fluorescent in situ hybridization analysis can be us ed to effectively analyze rare fetal aneuploid nuclei in enriched flow -sorted cells isolated from maternal blood.