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1 QF-PCR stand-alone prenatal diagnosis: the initial London experience. Caroline Mackie Ogilvie Cytogenetics Department Guy’s Hospital London.

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Presentation on theme: "1 QF-PCR stand-alone prenatal diagnosis: the initial London experience. Caroline Mackie Ogilvie Cytogenetics Department Guy’s Hospital London."— Presentation transcript:

1 1 QF-PCR stand-alone prenatal diagnosis: the initial London experience. Caroline Mackie Ogilvie Cytogenetics Department Guy’s Hospital London

2 2 Guy’s QF-PCR data Total samples tested: 23,311 CVS6729 (28.9%) AF16582 (71.1%) 97% of samples receive a result within one working day

3 3 Should we karyotype pregnancies at risk of Down syndrome? 32,674 pregnant women having invasive PND in London/South East 24,891 (76.2%) were referred for exclusion of Down syndrome others at risk of single gene disorders or complex chromosome abnormalities

4 4 24,891 pregnancies referred for exclusion of T sex chromosome abnormalities 153 other abnormalities

5 5 Good prognosis : – balanced rearrangements – variant regions Uncertain prognosis : – small marker chromosomes – mosaic anomalies Poor prognosis – non-mosaic genomic imbalance Abnormal karyotypes:

6 6 Trisomy risk referrals SexGPUPPP n n=24, % 0.39%0.15%0.07%

7 7 Poor Prognosis n = 18   1 liveborn (10q del) minor facial dysmorphism but normal development at 20 months   2 miscarried   4 outcome unknown, of which 1 = T16, 2 = 46,XX,del(18), 1=46,XX,add(9)   11 TOP (61%)

8 8

9 9 Advantages of QF-PCR stand-alone testing uncertain or harmless karyotypes not detected, reducing anxiety and follow-up studies no residual anxiety while waiting for karyotype results better use of resources

10 10 New service May 2007 All abnormal QF-PCR results followed up by karyotype analysis

11 11 Criteria for karyotyping Clinical indication, viz: structural abnormality on U/S 2 or more soft markers for trisomy 21 nuchal measurement >3mm at below 14 weeks gestation nuchals measurement >6mm for gestations >= 14 weeks family history of chromosome rearrangement

12 12 Data from 3 London labs 01/05/2007 – 30/11/2007 Consortium samples only

13 13 AF samples n=1502 CVS samples n=628

14 14 AF abnormals n=122 CVS abnormals n=135

15 15 Abnormalities not detected by QF-PCR Detection rate in karyotyped AF3% Detection rate in karyotyped CVS7% No abnormal babies reported to date.

16 16 One pregnancy: QF-PCR only at CVS ultrasound showed severe IUGR and abnormal placenta at 26 weeks follow-up amnio: mos tetraploidy pregnancy terminated fetal blood showed normal karyotype Tetraploid cell line probably confined to placenta leading to placental insufficiency Abnormalities not detected by QF-PCR

17 17 NT >3mm 3mm<4mm “An alternative strategy whereby qf-PCR is the main method of analysis and full karyotyping is reserved for those cases with a minimum fetal NT thickness of 4 mm would require full karyotyping in 10.1% of the cases, would identify 99.0% of the significant abnormalities, and would cost 60% less than full karyotyping for all.” Chitty et al. (2006) BMJ 25;332(7539):452-5.

18 18 NT >3mm 3mm<4mm

19 19 NT >3mm 3mm<4mm 2 abnormal karyotypes in this group 47,XY,+22 47,XX,+mar[19]/46,XX[28] –v small non-satellited marker, apparently all heterochromatin –?CPM –follow-up amnio and parental bloods requested, but not forthcoming –pregnancy terminated

20 20 Collaborators Guy’sNEL Regional Cyto Lab NWT Regional Cyto Lab (GOSH) (KGC) Kathy Mann Jonathan Waters Richard Ellis Zoe Docherty Melissa Holloway Janine Burbridge Sandra Edwards Sandra Edwards Deborah Morrogh Deborah Morrogh


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