Detection of mosaicism for primary trisomies in prenatal samples by QF-PCR and karyotype analysis.
OBJECTIVE
QF-PCR can be used to rapidly diagnose primary trisomy in prenatal samples. Our objectives were to estimate the prevalence of primary trisomy mosaicism for chromosomes 13, 18 or 21 in a cohort of prenatal samples, and to compare and contrast the detection of this mosaicism using both QF-PCR and karyotype analysis.


METHODS
Data was collated from all prenatal samples displaying mosaicism for a primary trisomy between June 2000 and March 2004. Levels of mosaicism were estimated and samples were categorised according to the cell population in which the mosaicism was detected.


RESULTS
In a total of 8983 samples, 18 samples (0.20%) displaying mosaicism were detected, including trisomy 13 (three samples), trisomy 18 (seven samples), trisomy 21 (seven samples) and mosaic triploidy (one sample). This included 7 amniotic fluid and 11 chorionic villus samples. Mosaicism was detected by QF-PCR in 12 samples and by karyotype analysis in 8 samples.


CONCLUSIONS
QF-PCR can detect mosaicism when the abnormal cell line contributes at least 15% of the whole sample. Use of both karyotype and QF-PCR analysis leads to the detection of more cases of mosaicism than either test alone.
Donaghue
Celia
C
Cytogenetics Department, Genetics Centre, Guy's and St Thomas' Hospital Trust, London, UK. celia.donaghue@gstt.sthames.nhs.uk
Mann
Kathy
K
Docherty
Zoe
Z
Ogilvie
Caroline Mackie
CM
D000328:Adult; D000649:Amniocentesis; D002478:Cells, Cultured; D015193:Chorionic Villi Sampling; D002877:Chromosomes, Human / Q000235:genetics*; D002882:Chromosomes, Human, Pair 13 / Q000235:genetics; D002887:Chromosomes, Human, Pair 18 / Q000235:genetics; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics; D004314:Down Syndrome / Q000175:diagnosis / Q000235:genetics; D005260:Female; D005453:Fluorescence; D006801:Humans; D007621:Karyotyping; D009030:Mosaicism; D016133:Polymerase Chain Reaction / Q000379:methods*; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D014314:Trisomy / Q000175:diagnosis* / Q000235:genetics