Direct detection of fetal cells in maternal blood: a reappraisal using a combination of two different Y chromosome-specific FISH probes and a single X chromosome-specific probe

Abstract

We have recently explored the detection of circulatory male fetal cells directly in maternal whole blood samples by fluorescence in-situ hybridization (FISH). In order to improve the efficacy of fetal cell detection, we have now examined whether this could be enhanced by the use of two different Y chromosome-specific FISH probes (alpha-satellite and classical satellite III regions) in combination with an X chromosome-specific FISH probe. Nineteen maternal blood samples (median gestational age = 28 weeks, range = 12-37 weeks) were examined in a blinded manner. No enrichment procedure was performed. Following hypotonic treatment and Carnoy's fixation, total nucleated cells were examined by two color FISH with a single X and two Y chromosome-specific probes. Nine cases were examined in parallel by conventional XY-FISH. Fetal cell detection was superior when using two Y chromosome-specific probes (specificity = 75%; sensitivity = 91%) when compared to the conventional XY-FISH approach (specificity = 50%; sensitivity = 60%). Male fetal cells can be detected in most maternal blood samples examined. Specificity and sensitivity is improved when using a combination of single X and two Y chromosome-specific probes when compared to a conventional XY-FISH protocol.