Pp. Pandya et al., RAPID DETECTION OF CHROMOSOME ANEUPLOIDIES IN FETAL BLOOD AND CHORIONIC VILLI BY FLUORESCENCE IN-SITU HYBRIDIZATION, British journal of obstetrics and gynaecology, 101(6), 1994, pp. 493-497
Objective Evaluation of fluorescence in situ hybridisation in the dete
ction of numerical aberrations involving chromosomes X, Y, 13, 18 and
21. Setting Harris Birthright Research Centre for Fetal Medicine. Subj
ects and methods Chorionic villi (n = 45) or fetal blood (n = 34) were
obtained from 79 pregnancies undergoing fetal karyotyping at 10 to 39
weeks of gestation because of ultrasonographic markers of fetal chrom
osomal abnormality. Karyotyping was performed by both traditional cyto
genetics and fluorescence in situ hybridisation, using commercially av
ailable kits which utilise a heterochromatic Y probe and the alpha sat
ellite repeat probes for chromosomes X, 18, and 13/21. The frequency d
istributions of the number of signals obtained by fluorescence in situ
hybridisation in the chromosomally normal and abnormal fetuses were c
ompared. Results Traditional cytogenetic analysis demonstrated that th
e fetal karyotype was normal in 47 cases and abnormal in 32 (including
24 with trisomies 21, 18 or 13, three with triploidy, one with Turner
s syndrome and four with translocations, deletions or mosaicism). With
fluorescence in situ hybridisation it was possible to obtain accurate
diagnosis of trisomy 18, Turners or triploidy within six hours of sam
pling; signal distributions with these chromosomal abnormalities were
very different from those of normals. However, for trisomies 21 and 13
there was an overlap in values with those from normals. Conclusions I
n detection of fetal numerical chromosomal abnormalities the use of th
e combined 13/21 probe cannot provide sufficiently accurate results to
justify abandonment of traditional cytogenetics in favour of fluoresc
ence in situ hybridisation.