FETAL CELL DETECTION IN MATERNAL BLOOD - A STUDY IN 236 SAMPLES USINGERYTHROBLAST MORPHOLOGY, DAB AND HBF STAINING, AND FISH ANALYSIS

A protocol to detect fetal nucleated red blood cells (NRBCs) was teste d in 217 pregnant women and in 19 nonpregnant controls. All the pregna nt women were sampled after chorionic villus sampling (CVS); 20 were a lso sampled pre-CVS. NRBC recognition was based upon morphology by usi ng staining of hemoglobin with 3,3-diaminobenzidin (DAB) or by immunoc ytochemical staining for fetal hemoglobin (HbF), This was combined wit h FISH analysis for both the X- and Y-chromosomes on the same cells. P rogressive refinement of the methods increased the number of cases whe re NRBCs were detected from 53% (DAB) to 75% and 78% for DAB and HbF s taining, respectively, with on average 43 NRBCs (range, 1-220), DAB ga ve a slightly higher yield than HbF in the lower cell count range (< 2 5), In 6 out of 18 controls, NRBCs were detected with DAB, vs. 1 out o f 19 (5%) with HbF, FISH analysis in 41 cases resulted in correct sex prediction in 80% (DAB) and 89% (HbF), respectively. Our data demonstr ated an increase of cases with NRBCs (30% to 75%), as well as a rise o f the mean number of NRBCs (6 to 29 cells), after CVS, We conclude tha t DAB staining is a straightforward way to screen for the presence of NRBCs in maternal blood, but is not specific for NRBCs of fetal origin . HbF immunophenotyping is a reliable marker for fetal NRBCs, which de tected slightly fewer NRBCs than DAB-staining, but improved sex predic tion and significantly reduced false-positive results. CVS at 10-13 we eks of gestation causes a significant increase of NRBCs in maternal bl ood. These data indicate that further refinement of NRBC detection is needed before application of noninvasive prenatal diagnosis using mate rnal blood is feasible. (C) 1998 Wiley-Liss, Inc.