False-positive diagnosis of trisomy 21 using fluorescence in situ hybridisation (FISH) on uncultured amniotic fluid cells.
An amniocentesis was performed on a 22-week pregnancy following the detection of foetal abnormalities on ultrasound. A rapid aneuploid screen using fluorescence in situ hybridisation on uncultured amniotic fluid cells revealed 3 signals for chromosome 21, consistent with trisomy 21. In situ metaphase cultures revealed a 46,XY normal male karyotype. These discordant results may be explained by a sub-standard batch of the commercially available probe or alternatively, a very specific variation within the sample interacting with the probe. Alternative strategies are proposed in order to safeguard against inappropriate clinical action as a consequence of discordant results.
George
Alice M
AM
Cytogenetics Department, LabPlus, Auckland Hospital, Auckland, New Zealand. aliceg@adhb.govt.nz
Oei
Paul
P
Winship
Ingrid
I
D000328:Adult; D000649:Amniocentesis; D000653:Amniotic Fluid / Q000737:chemistry* / Q000166:cytology; D002478:Cells, Cultured; D004314:Down Syndrome / Q000175:diagnosis*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D011247:Pregnancy; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal