Risk of false-positive prenatal diagnosis using interphase FISH testing: Hybridization of alpha-satellite X probe to chromosome 19

FISH analysis of uncultured interphase amniotic fluid cells from a male fet us revealed two signals using an alpha-satellite X-chromosome DNA probe. On e of the signals was much smaller than the other. It was subsequently shown that the normal sized signal was located on the X chromosome and the small er signal was located at the centromere of chromosome 19. This hybridizatio n pattern was confirmed in the newborn infant and in his phenotypically nor mal father. The use of alpha-satellite DNA probes on interphase cells could result in false-positive errors due to rare variants such as the X-chromos ome alpha-satellite found on chromosome 19 in our patient. Copyright (C) 19 99 John Wiley & Sons, Ltd.